I have been using 10-30 Valvoline for awhile and then swapped to synthetic at which time I developed an oil leak. I changed my oil the other day since I was a few over due and my dad suggested 10-w40 so I went with it. Is this oil ok for my car? I have very little knowledge about oil, its affects and such so bear with me. Also would this effect my dyno numbers as opposed to a 10-w30 oil? I will be getting a few runs in soon. I have heard of some folks getting a few ponies after swaping to synthetic.

 

I would use 5w30 in winter and maybe 10w30 in summer with your car.

 

yeah, stick w/ 10W-30 can't go wrong

how did you find your oil leak? are you down on oil or just see that black stuff coating the back of your motor or tranny?

i use Mobile 1 syn and i have some oil coating, but i'm not losing oil, prob less than 1/2 qt between oil changes. must be a low leak rate on mine.

 

10w40 would be fine (in warmer weather), but keep in mind that 10w40 conventional oil will thin out to a 10w30 in about 2 to 3000 miles.

10w40 Royal Purple would be a good choice, it's a thinner 40wt oil that I believe will show better wear numbers than a 10w30 Mobil 1 or other 10w30s that are on the thinner end of the 30wt scale.

Another good choice would be Mobil 1's 0w40, especially since you could run this all year round. It's their European formula, and passes some very good tests. Autozone sells it I believe, or in Ontario there is a Noco dealer at Kipling/Queensway near Toronto.

If you really want to stick with 10w30 though, go with Amsoil, Redline or Royal Purple 10w30 as they are all formulated to be on the thicker end of the 30wt. I personally believe an oil at the high end of 30wt to low end of 40wt will show the best wear numbers in an LT1. I'm experimenting with that myself this year in my car, through oil analysis. The range of a 30wt oil is 9.3cst at 100c to 12.49 cst at 100c. For 40wt oil it's 12.5 to 16.29.

So it is my belief that these engines, and LS1s too, will show their best wear numbers (in analysis) with an oil somewhere in the 11 to 14cst range, or more specifically, 12-13. When my winter time oil interval is over with, I'm going to mix Schaeffer 10w30 with 15w40 in order to achieve a final viscosity of 12-13cst. I will take an oil sample a week after putting my mixture in to see what viscosity I'm at, and adjust (via topping up with more of one or the other) accordingly. I think the looser clearances of the LT1, combined with having higher mileage (close to 80k now) means I need just a little bit more viscosity. I don't think 15w50 or 20w50 is needed, but just a little bit thicker that's all. Oil analysis is the best way to find out for sure though if my hunch is correct.

 

I'd read this: http://mr2.com/TEXT/synth_oil.txt
You'll find that the thinner oil will work better. It's a long article but very informative.

 

I didn't have time to read that hugely long article but what do you mean thinner oil works better? For which engine? Every engine is different, some designs show better wear with 5w30/10w30, some show better wear with 10w40. It's not one size fits all. And if someone does short trips compared to another doing all highway, the right viscosity is different between them also. Honestly, the BEST way to determine which oil is right for you is to do oil analysis in your own car and compare the results.

 

If you have a basically stock motor in good condition, run under a variety of conditions but nothing too extreme, the factory's recommendation of 5W-30 is fine. And synthetic is preferred for almost everyone. But OTOH, that 5W-30 recommendation takes mileage into consideration more than most of us do and also figures that people will not take very good care of their car. Start it up and immediately drive it hard, for example. That's why they recommend a 5W rather than say a 10W. It's best when "average" use is considered.

Beyond that, a lot depends on where you live, how you drive, what mods you have, and how often you change your oil. For example, I set up my motor with slightly loose clearances, and it is not used in cold weather. Consequently, I use Mobil 1 15W-50. This would not be a good choice here in the winter, unless a car was kept in a heated garage, warmed up before being driven, and not short-tripped.

You get the picture? 5W or 10W-30 is fine for most people under most conditions. 0W-40 sounds like a better all around choice, and it may be if you change infrequently and use a high quality synthetic. Wide range non-synthetics should be avoided, for a variety of reasons. If you live where it gets very cold, get an 0W, and if it's really hot, get something that goes up to 40.

Rich Krause

 

Actuall when I park the car in the garage sometimes, when I go to leave I can usually spots a few oil droplets.

Thanks everyone for this insight. I wasn't aware that there was that much importance placed on the differnt oil. I change my oil right around 3k miles and have the basic bolt-ons. I don't race that much maybe once every week or so and its usually only for a second.