My LT1 is currently around 77K and when I have my next oil change the car will just be hitting 80K. I run nothing but Castrol 10w-30 in my car but I was wondering if it was worth changing to those oils that say they are made for engines with over 75K miles. I mean what do these other oils do that is different from regular oil?

 

80,000 means the motor is finally just broken in. I am sure someone will chime in with more useful info.

 

Not really. Most of your high mileage oils just have conditioners for seals, gaskets, whatever. They're not going to make your bearings wear any slower. Unless you're having problems with the oil you're using there's no real reason to change. The best plan is changing your oil every 3k miles, that will give it a longer life than anything else. I prefer Mobil 1 myself, I hate spending the cash for it but I can't go back since I've started using it.

 

Why? Have you noticed any difference when using mobil 1?

 

If you want to use M1 do not use the 5w-30 or 10w-30 instead try the 0w-40 or 5w-40 they are better choices IN THIS BRAND for the LT1. If you are a Castrol man you might try the 0w-30 Castrol Syntec specifically labled Made in Germany on the back lable. It might just the the perfect oil for the LT1 that everyone MISTAKENLY believes M1 5w-30 is.

 

If the number is like 0w-30, is that the same thing as SAE 30?

 

Generally the high mileage oils have additives to "swell" the seals up and help control leaks and also have detergents in them to clean out the engine a little. If you like Castrol I would keep using it as you probably won't benefit any from a high mileage oil.

 

Not at all. SAE 30 is a straight 30 weight oil, meaning it is always 30 weight, which isnt really good in cold weather. 0W-30 is 0 weight cold, and 30 weight hot. At least thats what im under the impression it means.

 

thats great, take a car that originally had 5w30 recommended for emissions reasons. put 80K miles on it and the increased bearing clearences that go with those miles. then start recommending oils that are not only thinner and dont stay on the bearings as well after shutdown, but also dont have the sheer strength of a true synthetic. great idea

and everybody wonders why they are spinning bearings once they start spinning their higher mileage shortblocks past 6200rpm.

the IHRA top stock class racers that are running these 0 weight oils are using real synth like royal purple and redline and are not running on the street. they are also limiting oil to the upper end of the motor because they are reducing the plunger travel in the lifters from 0.200" down to 0.010" and run bronze inserts in the lifter bores. i wouldnt recommend running these 0 weight oils for performance use unless all the below criteria are met

1. its a race car that doesnt have to run for more then a 1/4 mile at a time;
2. and the oil is at optimum temprature whenever its run;
3. with an engine built by someone who knows what they are doing;
4. and you are running a true synthetic....

the only way i would run the stuff in my car is if it were winter time, i was using a true synthetic (not MI or Castrol syntec) and i wasnt going to try to rev it.

 

Obviously you have NO idea about Castrol Syntec, and especially the German made 0W-30. Cuz if you did, you would take back that entire post. Use the search feature, its cool.

 

Oh, and Syntec is a TRUE synthetic, Castrol Syntec BLEND on the other hand, is not.

 

i ran castrol when it was a true synthetic, before they changed it. i was using the stuff when it came out in 1990. M1 used to be a true synthetic too. you might want to do some searching yourself. maybe talk to some oil engineers that are unbiased. i can give you some telephone numbers if you like.

 

and, did you ever notice that years ago you could not mix M1 or castrol syntech with nonsynthetic oils? then all of a sudden they changed. hmmm....wonder why? castrol first then after a lengthy legal dispute with castrol and a loss in court M1 changed the same way. now all of the other synthetic producers are having to say you can mix synthetic when they used to recommend against it.

 

Plus they'd be contradicting themselves with their "blended" oils that are intended to get your typical person to spend a little extra but can't justify the really high price of synthetic.

Personally I would never run 0w-30 in an LT1 unless I lived in the arctic, or I had my engine built and that was what was recommended. Stick to 5W-30, or if your pressure seems to be a little low in the hotter months you may want to go with 10W-40 to be on the safe side. Just keep in mind that straying too far from OEM specs could land you in trouble. Also, oil pressure itself is not a sign of how well your engine is doing- You want to keep a medium ground, one where you have good pressure so oil is forced everywhere, but not so much that there isn't any flow.

Just remember that if all these suggestions are confusing you then just stick with the recommended 5W-30, you can't go wrong with that.

And why do I choose Mobil 1? When you're watching your tach sit at almost 6k in 2nd while you're shredding your tires which oil would you choose? I scimp on certain things on my car, but oil isn't one of them. Too much to lose if it fails.

 

i think all the synth blend stuff is just marketing. and just because the M1 and syntec isnt 'real' synthetic, dont mistake that im saying they are not good. they are very good. but the long and the short of what ive been told by friends that work as engineers at one of the big 'extend your mileage' synthetic oil manufactures is this;

if you are going to change your oil/filter every 3 months/3K miles no matter what (like i do) its a waste of money to run any of the high dollar synthetics. in the race bike engines we run regular 10-30 or 20-50 depending on the ambient temp.

here's a good article. they tested a synthetic 5w20 and 10w30 and a regular 20w50. the average hp was bested by the 5w20 synthetic, but only by 2hp compared to the last place 20w50 petroleum oil. and it goes on to say that the thicker non synth has more stable oil tempratures.

http://www.carcraft.com/techarticles...ip/index2.html