7T1vette

That is exactly why you should use synthetic oils. Better gas mileage is a minor issue and not really significant financially. But having your car's engine live 250,000-500,000 miles [rather than 100,000] is a VERY good reason to do so. The only reason auto factories don't put it in new cars is simply...it costs more. They would choose to save a dime on production costs rather than to give you a better product. Some companies that offer long warranty plans ARE putting synthetic products in their cars...just because they know it will minimize long term warranty costs.

ThunderMaker

Is your engine a flat tappet or roller rocker set-up? If you look in the archives, you'll see lots of info and opinion about the need for zinc in the oil for flat tappet engines. I run mobile 1 in my STS and my '05 Suburban but I've been hesitant to put it in my "79 because of leaking and my flat tappet engine.

stingr69

As for pressure - the 20-50 weight will affect your pressure by causing it to go up, especialy at cold start up. Not so much because it is synthetic but because of the thicker viscosity that you are putting in there.

As for leaks - Yes, running synthetic on an old engine will probably leak more than sticking with conventional oil.

I have run synthetic in the past but I don't use it anymore.

-Mark.

Jud Chapin

If you are going to keep a car for many years, I think synthetic is the only way to go, especially since it is basically the same price as mineral oil when factoring in longer times between oil changes and fuel savings.

I'm Batman

There are actually a fairly large number of vehicles now that come with synthetic as the factory fill (including most sports cars). They'll usually have an oil fill cap with the logo of the recommended oil manufacturer. I think some cars will void the warranty if you use dino oil.

WESCH

Hi

having your car's engine live 250,000-500,000 miles [rather than 100,000]

Lets make some math. I drive about 5000 Miles per year with my 68 , sometimes more, often less. By only being able to make 100.000, this will bring it to 20 years. Yes, I wouldn't mind to get 25 Years at least.

But leaving synthetics in there for 15.000 Miles would mean in my case , not changing oil for 3 years. Well, as we all know, oil should be changed more often, at least once a year. So I guess in my case, I will stay with the old Dyno oil.

I tried to change over one summer and my 68 BB also showed several extra seepages. Changing back to Dyno solved this leaks again.

+ all the threads about worn cams due to modern oil usage in old engines, like already mentioned further up ?

Günther

captainmorgan

I replaced the oil pan gasket and rear main seal in my '77 because the main seal was leaking. I put synthetic oil in and it is still leaking. Maybe I will try and put conventional oil back in to see if it stops leaking.

Ron R

I'm pretty sure both the Z06 and Viper come with Mobil 1 in the motor. If it's good enough for them, it's good enough for me

69vettester

I tried it in My old sb engine , it leaked bad out the rear main seal and the valve covers. I got the valve cover stopped but not the rear seal. Imediately changed back to Dino and got the leak stopped after 400 miles, 2 oil changes and a couple cans of stop leak. Only way you would ever know is to try it, My 2centavos is it would leak . I agree with the others that say . Just not worth the hassle in a old style engine with 100+Mi.

Edit: Im definitely putting Mobil 1 full synth. In the New GMPP 383 Roller engine after 2 thousand Miles. of good Breakin.

cv67

Not sure I buy the school of thought about Mobil wrecking flat tappets.
Synthetic in my Z (4 non roller cams) and with 144k miles no signs of any problems. Never even smokes on startup and these dont use any valve seals. Im sold.

On a conventional SBC the lifter will rotate regardless due to the taper in the cam. Dont let anyone tell you its too slippery and the lifter wont rotate. If it doesnt you got more than an oil problem .