spxChrome

I just bought this 93 LS and it had 95,000 miles on it. The service history has shown that it has always had Mobile 1 Sythentic oil (dunno the wait) put in it. Now I am going to get the oil changed tommorow for the first time since owning the car and my dealership doesn't stock synthetic. They use 5/30 Castrol.

My question is should I switch over now to the castrol or should I go buy 6 qts of Mobile 1 Systhentic 5/30.

He said they would be glad to use the oil I bring? When I bought the 5/30 it said for New Cars and the 10/30 was for something else (can't remeber) and 15/35 for high performance.

I want to use what is best for my car but it is going to be a pain to go buy Mobile 1 5/30 each time.

Also, with high millage should I use a different weight now than 5/30?

*** I woudn't care about this if I just didn't read this excerpt from the lexus.com website. ***
Can I use synthetic engine oil in my Lexus vehicle during its break-in period?

Synthetic oil can be used at the first scheduled oil change. Please note that the use of synthetic oil does not extend the recommended oil change intervals. Please refer to the Lexus Owner's Manual Supplement for further information regarding the proper maintenance schedule for your specific vehicle.

If synthetic oil is used after that time, it should be the same SAE (Society of Automotive Engineers) weight specification and meet or exceed the API (American Petroleum Institute) grade specifications listed in the Owner's Manual. Even if synthetic oil is used, we do not recommend longer oil change intervals. Once synthetic oil is used, it is best not to switch back to petroleum-based oil.[B]

SharpLS-96

Not a good idea to switch back to regular conventional oil if the car has always had synthetic oil.

Use full synthetic oil 10/30 weight for high mileage cars over 80,000 miles.
Go buy 6 qts of 10/30 full synthetic oil either Mobil 1or Castrol and bring them to your mechanic.

spxChrome

Crap, I just bought 6qt case of synthetic Mobile 1 5/30? Think it will be ok to run that until the next change and then I can go to the 10/30?

SharpLS-96

5/30 is okay to use for now but in the future use 10/30 weight because of your mileage.

TomWahjudi

You can always return the 5W-30 and get 10W-30. I myself use Amsoil High Performance synthetic 10W-40 on my '95 LS, switch the car to synthetic when I bought it at 108k miles. Engine is as dry as it can be, no leak no seeps. Maybe I'll run the Series 2000 20W-50 for summer, but I haven't decided yet.

I found that 10W-30 is too thin for my turbocharged DSM (valve lifters tick) during the warmer months and I have run the Series 2000 20W-50 into the cold months on the DSM. No problem with the oil being too thick in cold temperature eventhough the specification said otherwise, that's what I like about synthetic. In your case, if you are concerned about oil leakage, go with Mobil1 15W-50 especially during warmer months. Switch to 10W-30 for cold months.

seanl

I've been running Mobil 1 5W30 since I bought my LS with 50K miles on it. A bit over 2 years ago. It doesn't consume any oil between changes. Why would I want to run 10W30 now that I'm at 82K miles? I don't really consider 80K miles 'high miles' on an engine that is designed to last 300k+.

The only difference between 5w30 and 10w30 is the cold flow characteristics, correct? I'd need a pretty compelling reason before changing to 10w30 on this car.

Thanks,

spxChrome

10/30 is a little thicker and will protect the engine parts better since they wear down over time.

when the engine is new everything is tight and smooth, therefore the 5/30 thinner oil is better.


weather and your daily commute has alot to do with it also, if you travel less than 10 miles a day the thinner may be better to lube the parts quicker because it takes a few minutes to get it flowing.

your climate/temp is obvious, thick for hot, thin for cold.

no silver bullet, each situation will require something different.

seanl

10w30 is only thicker than 5w30 at low temperature. Fully warmed up, they're the same oil.

I understand this principal very well, but for cold starts I believe that one would want the *thinnest* oil possible (5weight) to lubricate the internals. For a hot engine, your theory would apply if you were comparing 5w30 to say the heavier 15w50.

At our knowledge level, oil choice *is* very subjective. I personally like running 5w30 in the all alum LS400's engine at my current mileage.

persian451

I use chevoron 20/50 or valvoline high RPM 20/50...

kreativ

If that were the case, I think we'd all be running 0W-30. 10W-30 is more stable (less prone to breaking down), has a better NOACk value, and has less VI improvers than 5W-30. After all, something has to give to improve an oil's range.

In a warm weather climate, 10w30 appears to be the better choice.

For synthetic, a 10w30 synthetic flows better than 5w30 dino anyways.

I see no reason for you to switch from Mobil 1 5w-30 though. If you were running dino oil, it'd be worth a thought.

seanl

Thanks kreativ, that's the kind of detailed answer I'm looking for.

Regards,