97Transam123

My car has 77k miles on it and i usually Quaker State peak performance 10w 30 should i really consider switching over? misixing it or just totally changing it over?

Terran2k

I just switched from 5w30 mobil 1 to 0w40 mobil 1. was going to switch too 0w30 Castrol (german made) but figured i've been using mobil this long. might as well stick with it, for now anyway.

Red96Lt1

I don't suppose they make a high mileage synthetic?

ImportKILLER

German Castrol is good stuff.

eagleknight97

Valvoline makes a high mileage synthetic, and I put it in my car last oil change, first time ive used it, so well see how that works.

96capricemgr

The only way switching to synthetic will cause problems is if varnish and dirt are the only things keeping the thing from leaking, I highly doubt any of you here are in that position. When switching oils I would however recommend keeping the first interval to 3K and changine the fiter after say the first 1K, because sometimes switching oils tends to flush out deposits from the old oil. On the oils being discussed here After a little reading about results with RP street I would not subject and engine to that stuff the race stuff is good though. On M1 I would strongly discourage the 5w30 and 10w30 specifically, the 0w40 and 5w40 are much better choices from this brand for this motor. Saying Amsoil is the best is flat out wrong, there is no best oil because different applications react differently and there is more to it than just weight. As an example M1 5w30 is actually a poor choice for an LT1 based on wear metals found in oil, does this mean it is a bad oil, no because I have also seen wonderful results(again by analysis) from it's use for 15K in a VW 1.8T, that is right a 15K mile oil change and it looked from an analysis standpoint, on the LT1 it shows high wear though because it runs toward the very low end of 30weight and pretty quickly even becomes a 20wt. with use, the LT1 is proven to want something thicker which could even be just another brands 30 wt.. The German made Castrol Syntec 0w30 shows some of the very best results for the LT1, good luck finding it.

Red96Lt1

So why do they recommend 5W30 on the filler cap?

n2ceptor

SAE 5W-30: is the most recommended grade in today's new cars. API Certified Gasoline Engine Oils and meets Energy Conserving Standards.

LameRandomName

No, it is not true.

What CAN happen is that after a lifetime of running Dino oil, you may have a leak somewhere, such as in the pan gasket for instance, that is currently plugged with sludge. Synthetic oil has a stronger "detergent" effect than Dino. So... you replace your oil, clean away the sludge and suddenly a pre-existing leak becomes active, or perhaps just MORE active.

However, it wont hurt the mechanical parts at all.

One thing I strongly suggest when changing over to synthetic on a high mileage engine is that you change your FILTER at 500 miles and again at 1500 and 3000, at which point you go to a normal 3000 mile filter change.

The reason for this is due to the detergent effect that I was talking about. It cleans out your engine and all that crud can plug your filter pretty quickly.


BTW, as an additional testimony to synthetic, I was over at my best friend's place last night, and he has an old chevy dump truck with the full-floating 14-bolt rear end. He changed over to synthetic differential fluid recently and saw... get this: A TWO MPG INCREASE, just from changing the gear oil.

96capricemgr

5w-30 is CAFE talking, every fraction of a MPG a manufacturer can squeak out of every model pays off. But 5W-30 in a brand other than Mobil 1 may be just fine, it is Mobil 1s 30weights specifically that are too thin for this motor. Amsoil for instance runs thick in the 5 and 10w-30. Analysis proves the LT1 likes a high 30wt. to low 40wt., M1 is a low 30wt. Besides the same guys who recommend the 5w-30 and that spec M1 for the Vette are the same ones that brought you the non-vented Opti and the PWM in the auto trannies, so clearly they make mistakes and compromises, this is just an example of that.

n2ceptor

Interesting reading....

http://www.z06vette.com/forums/showt...threadid=45423

96capricemgr

The oil site linked in that thread is where I do my reading.

n2ceptor

This One????

http://www.bobistheoilguy.com/

LT1Squirrel

so the M1 10w30 im running isnt good for me engine?

n2ceptor

You have to decipher what information is given; whether its facts, opinions or possibly false statements and decide for yourself what is best for you...

I have been running M1 15w50 summer and M1 5w30 winter.... I am going to try the German 0w30 Castrol this winter and see how it performs....JMO