xrav22

castrol gtx 20-50 @150,000 running like a top.

BDKesling

Haven't changed my oil yet (due in 700 miles), but the guy I bought it from ran 10w-40 castrol gtx. 254k miles and no leaks. He said it leaked all over the place with synthetic.

pavlova1000

96 lt1, 5w30 mobile one synthetic. Changed religiously every 3000 miles (daily driver year round) Opti spark leaked at 103k miles. Just changed that out so leak is gone up front. Now to deal with the transmission output shaft seal.

DGXR

Mobil 1 5w30 full synthetic and M1-102 filter
Changed every year or 7500 miles, whichever came first
106000 miles
This info according to previous owner, one of those honest good old boys, and the engine runs and sounds fantastic -- no ticking or knocking or problems of any kind.

Not sure about the Valvoline engine guarantee, haven't heard of anyone bothering to keep the records required by the program let alone actually trying to cash in on a new engine (or repair of damage due to oil-related failure). But I suppose any modern engine oil could guarantee that an engine will run for a certain number of miles if it's changed regularly. Heck, some engines have gone 300k miles running only store-brand petroleum engine oil -- Flag, O'Reilly, etc. -- so long as it has the API donut and starburst symbols on the bottle. The key is regular maintenance.

Corvette Chris

I use the regular M1, but thats my interval as well

VRSCDX

Mobil 1 10w-30 in the 96 Vette(73000) and the 2004 Ram 1500! changed every 3000 miles religiously!!! Never any leaks caused by oil! Intake is leaking on the car but not the oils fault!!!

C4in mesa

Castrol 20W-50 K&N filter. Filter is IMPORTANT. No $4 Fram ! Change every 2000 miles. I run this thicker oil in the summer due to my oil temps running as high as 260 degrees. I can't find thicker synthetic. Not one store carries it. Besides the owner of the shop who rebuilt my motor said it doesnt matter synthetic or regular oil just change it !!!!

aklim

At 2000, you can run most syn or regular. It won't matter. If you want to stretch the oil change out, my samples sent to Blackstone for analysis seemed to point out that synthetic could go longer.

C4in mesa

I totally agree ! However ny oil temps climb to 260 degrees on HOT days. I feel 20W-50 is a better choice under those conditions. All I can find at Walmart or Autozone is 5W-30 or 10-30 Mobil 1

lt4obsesses

The heavier 20/50's in hot climates may be good for the Gen I L98 cars, but for those with the LTx cars I don't think it would be a good idea. The clearances and tolerances are alot tighter in these engines, not to mention the roller lifters. It just seems if the oil is too thick you'd be risking oil starvation at the crank and lifters.

aklim

I still think the best test for whether the oil is worth is is with an analysis. That way, you are not throwing oil out that can go further or using oil longer than it should.

C4in mesa

I asked the guy or shop that rebuilt the motor and guaranteed it about 20W-50. He said its all he uses year round. Keep in mind its extremely hot here half the year. I am gonna try to locate heavier synthetic oil. But bottom line regardless of standard or synthetic is to change it often. 2500 miles and 5000 synthetic. I believe a quality filter is important too.

1991Z07

I use 20W50 full synthetic in mine...have for the entire life of the car. My "race motor" has over 45k on it, and it's strong. No oil blow by in the valve train or past the rings.

One of our club members has an old 70's Impala wagon he uses to tow to events. It has over 300k miles on the original block. It's had 2 head rebuilds...for guides/seals and putting hardened seats so it could run unleaded fuel. Last time I saw him fooling with it he had the pan off and was checking the bearings...they still looked fresh.

In Stillwater at the Mercury Marine plant they used to have an LT5 test engine on display cut up...they had the equivalent of 300k miles on the dyno with it, and the bearings showed ZERO wear. You could still see the cross hatches in the liners from the honing.

Synthetic is THE way to go if your seals are up to it...as long as they don't leak it out, use it.

bjankuski

L98 and LTx run the same clearances.

jabez

I will use any oil with the GM4718 cert on it. Will change every 10,000 miles or once a year.