Low oil pressure with new oil?
07-23-2014, 03:32 PM
#1
Le Mans Master
Thread Starter
Low oil pressure with new oil?
I changed oil in the car yesterday and when i started the car i had 35-40 on the meter,but today when i start and run the car i have 25-30 on the meter,at idle its at 20?
There was 15w40 in it and i have 20w50 in it now
Im starting to wonder if the gauge is bad i have a new pressure sender on the motor
There was 15w40 in it and i have 20w50 in it now
Im starting to wonder if the gauge is bad i have a new pressure sender on the motor
07-23-2014, 04:24 PM
#2
Pressure is very much dependant on oil temperature but there's nothing wrong with the pressures you mention.
20W50 is not the best choice for your climate.
20W50 is not the best choice for your climate.
Last edited by Mike Ward; 07-26-2014 at 10:21 AM.
07-23-2014, 05:09 PM
#4
Yes, I know it was hot today in Sweden, I was just speaking to a friend in Åseda who made a similar comment. 93F = 33*C.
20W50 is still not required or of benefit compared to 10W30.
20W50 is still not required or of benefit compared to 10W30.
07-23-2014, 05:16 PM
#5
Le Mans Master
Thread Starter
Ok so its better to run with 10w30 then?,it was just so strange that it changed over night?
Thought it wouldnt be so much differerence between 15w40 and 20w50
Thought it wouldnt be so much differerence between 15w40 and 20w50
07-23-2014, 09:23 PM
#6
Yes. Seems as if the current thinking is that the thinner oil gets to the bearings sooner after a cold start, where 90 to 95% of wear occurs in the first ten seconds or so of operation.
07-24-2014, 12:12 AM
#8
Team Owner
Oil pressure at idle on a Chevy V8 when COLD could be in the 30-40 range (with 10W30 grade, which is the recommended choice by GM). When the engine is WARM, this could drop to around 15 psi...give or take (10-20psi). The thicker the oil you choose, the higher the oil pressure will be.
But, there is no benefit from running thick oil in a Chevy V8 engine...unless you live in the tropics. Also, more 'work' by the oil pump means more $$$ at the fuel pump...
Use 10W30 in your engine. Idle oil pressure should be 10-20 psi; highway cruising oil pressure should be 35-45 psi.
But, there is no benefit from running thick oil in a Chevy V8 engine...unless you live in the tropics. Also, more 'work' by the oil pump means more $$$ at the fuel pump...
Use 10W30 in your engine. Idle oil pressure should be 10-20 psi; highway cruising oil pressure should be 35-45 psi.
07-24-2014, 06:37 PM
#9
Le Mans Master
Thread Starter
no change with new oil,then i put my old mechanical gauge back on and its perfect so my 1 month old oil pressure sender is broken... good quality.... 
07-24-2014, 07:03 PM
#10
Le Mans Master
There should not be much difference between 15W and 20W oils with pressure. I would suspect the gauge or the filter causing the difference.
As for the oils, 20W-50 is perfectly acceptable for Gen 1 SBC V8's down to 32 degrees F-it's in my 78 owners manual-not debatable. As for 5W-30/10W-30 oils for a SBC Gen 1 with a flat tappet cam-absolutely NOT unless it has the correct amount of ZDDP. Do not use Diesel oils.
I am currently running in my just built L-82 355 with a ROLLER cam for the first 500 miles, Driven Oil, HR Conventional 15W-50, hot Rod motor oil designed specifically for hot rods and classic vehicles-High ZDDP-per my builders recommendation. I intend to run Mobil 1 0W-40 after the 500 miles-1,000 PPM ZDDP.
From the March 2014 Vette magazine article posted in the oil sticky, ALL About Oil article, I quote from Mobil "For older Vettes, we recommend Mobil 1 15W-50 street oil for its higher zinc content."
Hope that helps!
As for the oils, 20W-50 is perfectly acceptable for Gen 1 SBC V8's down to 32 degrees F-it's in my 78 owners manual-not debatable. As for 5W-30/10W-30 oils for a SBC Gen 1 with a flat tappet cam-absolutely NOT unless it has the correct amount of ZDDP. Do not use Diesel oils.
I am currently running in my just built L-82 355 with a ROLLER cam for the first 500 miles, Driven Oil, HR Conventional 15W-50, hot Rod motor oil designed specifically for hot rods and classic vehicles-High ZDDP-per my builders recommendation. I intend to run Mobil 1 0W-40 after the 500 miles-1,000 PPM ZDDP.
From the March 2014 Vette magazine article posted in the oil sticky, ALL About Oil article, I quote from Mobil "For older Vettes, we recommend Mobil 1 15W-50 street oil for its higher zinc content."
Hope that helps!
07-24-2014, 11:21 PM
#11
Team Owner
The Chevrolet Chassis Service Manual for 1971 (and other 70's vintage vehicles) presents a chart of "RECOMMENDED SAE VISCOSITY NUMBER" vs. ambient temperature (F). The temp part of the chart runs from -30*F to +100*F. The recommended oil weights for those temperatures range from 5W-20 and 5W-30 (between -30 and +20); 10W, 5W-30, and 10W-40 (between 0 and +60); and 20W, 10W-30, 10W-40, and 20W-40 (between +20 and +100).
NOWHERE on that chart is any 50W oil shown as "recommended" by GM or Chevrolet.
Obviously, anyone can use anything in THEIR car. But using a heavy weight oil in an engine that wasn't designed for it, nor needs it, is unnecessary and causes loss of engine efficiency (for no benefit) and more work for the oil pump.
Just sayin'....
If you have a racing engine or have modified your engine for racing use, heavier weight oil might be better for SURVIVAL during prolonged, hard use. If you have a 'relatively' stock engine, it would be best to use what the manufacturer has used during testing of those engines and then recommends.
NOWHERE on that chart is any 50W oil shown as "recommended" by GM or Chevrolet.
Obviously, anyone can use anything in THEIR car. But using a heavy weight oil in an engine that wasn't designed for it, nor needs it, is unnecessary and causes loss of engine efficiency (for no benefit) and more work for the oil pump.
Just sayin'....
If you have a racing engine or have modified your engine for racing use, heavier weight oil might be better for SURVIVAL during prolonged, hard use. If you have a 'relatively' stock engine, it would be best to use what the manufacturer has used during testing of those engines and then recommends.
Last edited by 7T1vette; 07-24-2014 at 11:25 PM.
07-26-2014, 07:11 AM
#12
Le Mans Master
The Chevrolet Chassis Service Manual for 1971 (and other 70's vintage vehicles) presents a chart of "RECOMMENDED SAE VISCOSITY NUMBER" vs. ambient temperature (F). The temp part of the chart runs from -30*F to +100*F. The recommended oil weights for those temperatures range from 5W-20 and 5W-30 (between -30 and +20); 10W, 5W-30, and 10W-40 (between 0 and +60); and 20W, 10W-30, 10W-40, and 20W-40 (between +20 and +100).
NOWHERE on that chart is any 50W oil shown as "recommended" by GM or Chevrolet.
Obviously, anyone can use anything in THEIR car. But using a heavy weight oil in an engine that wasn't designed for it, nor needs it, is unnecessary and causes loss of engine efficiency (for no benefit) and more work for the oil pump.
Just sayin'....
If you have a racing engine or have modified your engine for racing use, heavier weight oil might be better for SURVIVAL during prolonged, hard use. If you have a 'relatively' stock engine, it would be best to use what the manufacturer has used during testing of those engines and then recommends.
NOWHERE on that chart is any 50W oil shown as "recommended" by GM or Chevrolet.
Obviously, anyone can use anything in THEIR car. But using a heavy weight oil in an engine that wasn't designed for it, nor needs it, is unnecessary and causes loss of engine efficiency (for no benefit) and more work for the oil pump.
Just sayin'....
If you have a racing engine or have modified your engine for racing use, heavier weight oil might be better for SURVIVAL during prolonged, hard use. If you have a 'relatively' stock engine, it would be best to use what the manufacturer has used during testing of those engines and then recommends.
Above is the exact page from my 78 owner's manual. I am not recommending 20W-50 (I have not used that weight oil in my 78 L-82 for 25 years) but clearly GM found it "acceptable" in 1978 like I stated earlier. Also, as stated earlier and which I have been using for years as outlined in the ALL About Oils article in the March 2014 Vette Magazine, Mobil, who I would assume knows a lot more about oil than most of us, clearly states that Mobil 1 15W-50 (1,200 ppm ZDDP) is the oil Mobil recommends for older C3's. Obviously a 5W/10W weight oil can also be used (as long as it has at least 1,200 PPM ZDDP-some say 1,000 PPM- for flat tappet cams), but most oils of this weight do NOT have adequate ZDDP.
My just rebuilt L-82 355 with a roller cam is currently running Driven 15W-50 per my builder's explicit direction-notice a theme here?…… I will be using Mobil 1 0W-40 European Formula after 500 miles-Group IV PAO True Synthetic-which is a great deal (builder concurs BTW)-$25 for 5 Qts
Last edited by jb78L-82; 07-26-2014 at 07:18 AM.
07-26-2014, 07:22 PM
#13
Team Owner
That [later] chart shows an arrow pointing to higher than 100*F...which the earlier chart did not have. I would assume that 20W-50 might be OK for areas having 100*F + days on a regular basis.
That would be the tropics or the middle East...and maybe Phoenix.
That would be the tropics or the middle East...and maybe Phoenix.
07-26-2014, 08:52 PM
#14
Le Mans Master
The 78 owners manual chart (above) shows that 20W-50 is appropriate according to GM from 20 to above 100 degrees and 10W-30, 10W-40 oils are appropriate from 0 to above 100 degrees. The Bar chart does NOT mean that 20W-50 should only be used in climates over 100 degrees.
Last edited by jb78L-82; 07-26-2014 at 08:55 PM.
07-26-2014, 11:49 PM
#15
Le Mans Master
My just rebuilt L-82 355 with a roller cam is currently running Driven 15W-50 per my builder's explicit direction-notice a theme here
I know you talked about this in another thread, I'm just a bit curious as to what the reasoning might be behind it.
07-27-2014, 06:07 AM
#16
Le Mans Master
I did ask him what the thinking is since I wanted to run Mobil 1 0W-40 European Formula (1,000 PPM ZDDP, True Group IV synthetic) right from the start. He explained that roller cam motors need break in at start up (this theory is explicitly stated in the All About Oil article from the March 2014 Vette Magazine article as well) and that the motor requires break in for the pistons/rings, etc just like any motor for the first few hundred miles. Conventional wisdom is that roller motors do not require break in-not true. He wanted a conventional oil with high ZDDP (thus Driven HR 15W-50) for faster break in and maximum wear protection for other engine parts-I used Driven Break In oil for 30 minutes prior to the Driven 15W-50 still in the engine. I proposed using Mobil 1 15W-50 (1,200 ZDDP) after the Driven Break In oil for the 30 minutes and he said that using the Mobil 1 15W-50 for the first 500 miles would not allow adequate wear for the some parts (Superior lubrication and anti wear properties (theme here about synthetics-BTW) and I would need much longer mileage to break in the motor. I did not discuss why 15W-50 versus a 10W-30 after the 30 minute break in, for example, simply since I do not buy into the theory that using a 15W/ 20W weight oil for a Gen 1 SBC is a bad, especially in warm weather. He does agree with me that Mobil 1 0W-40 Euro Formula is a GREAT Group IV true synthetic and is a good choice after the Driven HR 15W-50 mileage break in.
With all that stated, if I had not paid some $$ for his work on the bottom end, I probably would have used Mobil 1 0W-40 Euro Formula after the 30 minute break in but since I was concerned if the engine developed any problems along the way, it would be tough to go back to him about an engine issue, IF i had not followed his directions explicitly.
The other reason I favor Mobil 1 0W-40 Euro Formula besides what I have already stated is that I find it somewhat comical about folks discussions about oil weights. If you use a superior synthetic in combustion engines of any type, the issue of oil weight is somewhat irrelevant. What do I mean? My 2001 Grand Prix (160,000 miles) and 2008 Chrysler 300 3.5L V6 (110,000 miles) both run Mobil 1 0W-40 (not the specified 10W-30) and neither uses a drop of oil. I also run the same Mobil 1 0W-40 in my 10 Z06-not Mobil 1 5W-30 specified by GM-European Z06's used 0W-40.
Lastly, my gas generator, Kohler engine on my riding mower, and 1988 Toro Snowblower all specify Straight 30 or 10W-30 engine oil. They each have so many hours on them, I can't recall but I have never run those weights of oil (Mobil 1 5W-30 and now Mobil 1 OW-40) and I ran a full synthetic oil right from the first firing of each of them (suppose to use conventional oil and straight weight). Not one of my engines has ever failed or used an OZ of oil. My oil choices are all based on personal experience over 30 years, synthetic chemical logic, and recommendations from the experts (Mobil, etc).
Hope that helps!
Last edited by jb78L-82; 07-27-2014 at 06:15 AM.
07-27-2014, 10:51 PM
#17
Le Mans Master
Good question.
I did ask him what the thinking is since I wanted to run Mobil 1 0W-40 European Formula (1,000 PPM ZDDP, True Group IV synthetic) right from the start. He explained that roller cam motors need break in at start up (this theory is explicitly stated in the All About Oil article from the March 2014 Vette Magazine article as well) and that the motor requires break in for the pistons/rings, etc just like any motor for the first few hundred miles. Conventional wisdom is that roller motors do not require break in-not true. He wanted a conventional oil with high ZDDP (thus Driven HR 15W-50) for faster break in and maximum wear protection for other engine parts-I used Driven Break In oil for 30 minutes prior to the Driven 15W-50 still in the engine. I proposed using Mobil 1 15W-50 (1,200 ZDDP) after the Driven Break In oil for the 30 minutes and he said that using the Mobil 1 15W-50 for the first 500 miles would not allow adequate wear for the some parts (Superior lubrication and anti wear properties (theme here about synthetics-BTW) and I would need much longer mileage to break in the motor. I did not discuss why 15W-50 versus a 10W-30 after the 30 minute break in, for example, simply since I do not buy into the theory that using a 15W/ 20W weight oil for a Gen 1 SBC is a bad, especially in warm weather. He does agree with me that Mobil 1 0W-40 Euro Formula is a GREAT Group IV true synthetic and is a good choice after the Driven HR 15W-50 mileage break in.
With all that stated, if I had not paid some $$ for his work on the bottom end, I probably would have used Mobil 1 0W-40 Euro Formula after the 30 minute break in but since I was concerned if the engine developed any problems along the way, it would be tough to go back to him about an engine issue, IF i had not followed his directions explicitly.
The other reason I favor Mobil 1 0W-40 Euro Formula besides what I have already stated is that I find it somewhat comical about folks discussions about oil weights. If you use a superior synthetic in combustion engines of any type, the issue of oil weight is somewhat irrelevant. What do I mean? My 2001 Grand Prix (160,000 miles) and 2008 Chrysler 300 3.5L V6 (110,000 miles) both run Mobil 1 0W-40 (not the specified 10W-30) and neither uses a drop of oil. I also run the same Mobil 1 0W-40 in my 10 Z06-not Mobil 1 5W-30 specified by GM-European Z06's used 0W-40.
Lastly, my gas generator, Kohler engine on my riding mower, and 1988 Toro Snowblower all specify Straight 30 or 10W-30 engine oil. They each have so many hours on them, I can't recall but I have never run those weights of oil (Mobil 1 5W-30 and now Mobil 1 OW-40) and I ran a full synthetic oil right from the first firing of each of them (suppose to use conventional oil and straight weight). Not one of my engines has ever failed or used an OZ of oil. My oil choices are all based on personal experience over 30 years, synthetic chemical logic, and recommendations from the experts (Mobil, etc).
Hope that helps!
I did ask him what the thinking is since I wanted to run Mobil 1 0W-40 European Formula (1,000 PPM ZDDP, True Group IV synthetic) right from the start. He explained that roller cam motors need break in at start up (this theory is explicitly stated in the All About Oil article from the March 2014 Vette Magazine article as well) and that the motor requires break in for the pistons/rings, etc just like any motor for the first few hundred miles. Conventional wisdom is that roller motors do not require break in-not true. He wanted a conventional oil with high ZDDP (thus Driven HR 15W-50) for faster break in and maximum wear protection for other engine parts-I used Driven Break In oil for 30 minutes prior to the Driven 15W-50 still in the engine. I proposed using Mobil 1 15W-50 (1,200 ZDDP) after the Driven Break In oil for the 30 minutes and he said that using the Mobil 1 15W-50 for the first 500 miles would not allow adequate wear for the some parts (Superior lubrication and anti wear properties (theme here about synthetics-BTW) and I would need much longer mileage to break in the motor. I did not discuss why 15W-50 versus a 10W-30 after the 30 minute break in, for example, simply since I do not buy into the theory that using a 15W/ 20W weight oil for a Gen 1 SBC is a bad, especially in warm weather. He does agree with me that Mobil 1 0W-40 Euro Formula is a GREAT Group IV true synthetic and is a good choice after the Driven HR 15W-50 mileage break in.
With all that stated, if I had not paid some $$ for his work on the bottom end, I probably would have used Mobil 1 0W-40 Euro Formula after the 30 minute break in but since I was concerned if the engine developed any problems along the way, it would be tough to go back to him about an engine issue, IF i had not followed his directions explicitly.
The other reason I favor Mobil 1 0W-40 Euro Formula besides what I have already stated is that I find it somewhat comical about folks discussions about oil weights. If you use a superior synthetic in combustion engines of any type, the issue of oil weight is somewhat irrelevant. What do I mean? My 2001 Grand Prix (160,000 miles) and 2008 Chrysler 300 3.5L V6 (110,000 miles) both run Mobil 1 0W-40 (not the specified 10W-30) and neither uses a drop of oil. I also run the same Mobil 1 0W-40 in my 10 Z06-not Mobil 1 5W-30 specified by GM-European Z06's used 0W-40.
Lastly, my gas generator, Kohler engine on my riding mower, and 1988 Toro Snowblower all specify Straight 30 or 10W-30 engine oil. They each have so many hours on them, I can't recall but I have never run those weights of oil (Mobil 1 5W-30 and now Mobil 1 OW-40) and I ran a full synthetic oil right from the first firing of each of them (suppose to use conventional oil and straight weight). Not one of my engines has ever failed or used an OZ of oil. My oil choices are all based on personal experience over 30 years, synthetic chemical logic, and recommendations from the experts (Mobil, etc).
Hope that helps!
I'm just courious what various builders do for what reasons.