Oil experts: is this correct?

[mkIIIman089]

Hi all, as you can see I'm new to the boards here, and I have a question about which oil is actually best for my 89 Toyota Supra turbo.

Toyota reccomends 10W-30 or 10W-40 from 0*F to (infinite)*F in the original owners manual. and 5W-30 for -20*F to 80*F weather conditions.

Now the enthusiast community swears on its life that the proper oil to use is 20W-50 synthetic year round. So I bought some Amsoil 20W-50 and I have been using that since I got the car a little over a year ago; and once warm the oil pressures are right in line with the Repair manual specs according to my aftermarket guage. More then 4.3psi at idle and a range (not sure of specifics at the moment) for 3k RPM.

Super Street as well had an article in which oil experts working for an oil company (I can't remember which one exactly) for a pro drag race team said that for the main bearing clearances that my motor runs, 20W-50 is the proper weight as well.

My car is not stock, I'm estimating I'm running about 300BHP from a stock 232BHP and my ultimate goal is 400BHP or just under.

I'm not the most in the know about all the advanced properties of the different weights of oils and which means what in the real world. So I was hoping someone could tell me that even though the main bearings according to the one tech and the community beliefs say 20W-50; if other parts of the motor (the head for instance) could have ports or tolerances that should run with 10W-30 instead. Or if oil has just become more advanced and higher weight synthetic oils can be used just as safely for the whole motor as dino oil from the early 80s of thinner weight.

Sorry for the long post but I wanted to give as much info as I could to aid in the answer. Thanks!

 

[LarryL]

I don't think that running 20w-50 will hurt, but the idea is to run a thinner oil like 10w-40 for better overall protections and a little better lubrication during startup. 5w-30 might be even better, especially if you use synthetic oil. I use 5w-30 synthetic in my wife's 850 Turbo Volvo. My thought is that fighting startup wear is important and I use 5w-30 instead of a heaver oil for that purpose. Modern oils are very good and even a 30 weight gives good protection. In my opinion, if you are not burning a lot of oil, 20w-50 is just not necessary. It's just too thick.

 

[Curious Kid]

With an engine that was designed to be thrashed at the stated load of 232BHP with a moderate life expectency, asking so much more will knock that expectency down some to eextent that measures arn't taken...it appears you are mindful of your endevor.

Staying on the subject of oil, I believe that pushing higher and higher output figures will only magnify the stress loads the lubrication points will see. This all makes me think of thermal strain which brings an oils HTHS figures to mind. A 20w-50 oil I imagine would easily have an HTHS number above 3.6, which in euro rating terms (ACEA), the oil meets A3/B3 qualification. These elevated numbers would given some reasurance that states of lubrication have a better likelihood of being closer to the mixed film/hydynamic film regimen rather than boundry lubrication as power is demanded (to an extent). This is in comparison to say the average 5/10w-30 with HTHS #'s of 3.1 or 3.2 (A1/B1).

As far as finding a weight of oil that enable HTHS figures greater then your typical 30 weights, yet still be able to flow well and provide a relatively easy time starting the engine in the cold...you could try Castrol syntec (GC) 0w-30 or there 5w-50, M1's 0w-40 and M1's t&suv 5w-40. There's many more but these are the ones I come across often in stores. Looking for the ACEA A3/B3 rating will ensure an HTHS@150 deg.c to be 3.5 or 3.6 cSt and higher.

I suppose I should have asked just how cold a temp do you see as for it seemed the question is whether it's safe to use a 20w-50, Yes? But as has been thrown around here, no oil seems thin enough at start-up. The only question that then remains concerning the point spread is the quantity of viscosity index improvers (VII's) that might be included as part of the oils add pack to enable the high at-temp weight (some oils can do this via esters and so forth instead of VII's, so the point spread isn't neccessarily a bad thing as many have though years ago. It's amazing how things have changed).

Outside of running UOA's to check for shear thinning of the oil (of it's VII's)among other things like fuel thinning and wear metals, one could opt for shorter oil change intervals than you would have on a stock engine. Depending on the amount of blow-by, this may still be a good consideration.

Sounds like you're engine's going to be a real torture device for just about any oil. Good luck and keep us posted.

One last thing...

 

[Trex101]

Schaeffer #9000 5w40 has a pretty high HTHS of 4.57, you may want to try this oil.

 

[Pablo]

There is nothing wrong with the oil you are using. The Amsoil Series 2000 20W-50 is a pretty amazing oil IMHO. Look at the low temp properties:

TRO

Almost like a dino 10W or 15W (better than some actually) - and on the 50 side like a 40 rather than a high 50, and a HTHS of 5.1. Have you run a UOA on this oil in your car? I would do this before changing oils.

Also I think the Amsoil 5W-40 would perform nicely, also.

 

[mkIIIman089]

The lowest temp I remember seeing last year was in the morning at -8*F which is pretty frigid, but Amsoil seem to state in their description that its not so bad...

What I'm gathering from your post primarily is that higher HTHS rating will provide greater high stress protection. So I checked into the oil I got and the HTHS rating is 4.9, with the Series 2000 that Pablo pointed out is 5.1. Both I'm assuming are quite high and will provide excelent protection. And as of right now the motor burns a tiny bit through valve stem seals, and leaks no oil and has no excessive blowby from anything I can tell.

I'm slightly confused about VII's. The only way to tell for sure is to use a UOA (what is that?) to see if they are of good quality or not?

I should add that right now the car has its old stock oil cooler setup which is based on pressure. However before I track the car (road course, not drag race) I will have an aftermarket cooler which will be thermostatically controlled.

One more thing as well, I am conceous of the fact that the oil is very thick on startup and I normally give it 30 seconds when its 50+*F outside, and about 3 or more minutes once it gets down below freeing temps of just idling to bring it up to some kind of temp. I always wait for the water temp to come fully up to temp with the thermostat open and my GReddy guage stops jumping so much before I lay into the throttle at all to get the turbo spooled. I normally do oil changes every 3k or 6 months. 6 months from Amsoil's reccomendation and 3k because its between the two figures Toyota gives; but towards the lower of 2500.

Thanks!

[ December 05, 2005, 08:00 PM: Message edited by: mkIIIman089 ]

 

[robbobster]

FWIW, I run 10W30 Mobil 1 in my Expedition. It's got a blower running 13 psi, and I tow, so my application is similar (high boost) though our engines are quite different.

10W30 was pretty much the consensus when I asked for suggestions in these forums.

 

[mkIIIman089]

Just was browsing different brands a lot of people use in the Supra community; and it would appear that RedLine is actually the best for multiple catagories (aside from VII which I don't know until I test I suppose). Let me know what you think:
http://www.redlineoil.com/pdf/4.pdf