I'm currently using Quaker State 10W40 (recommended by engine builder) dino oil in my 383. I was wanting to switch to Mobil 1 now. What weight should I use in synthetic?

I was looking at 15W50.

Right now the the psi jumps up to 60 psi on start up and then settles down to 32 psi at idle after 5-10 min of driving with the 10W40 dino oil.

This is on a 383 LT1 with 422 rwhp.

BTW, its 100 F outside here today.

 

Should be able to use the same weight. The viscosity is measured the same no matter what the oil is made of.

 

I would use a 40 weight still probably a Mobil1 0w-40. Sounds like the clearances are a little on the loose side but that's fine as long as you have enough oil in there.

Bret

 

Does Mobil 1 take longer to reach its operating temp viscosity than dino oil?

 

Only thing I can think of that would prevent that is low friction from the M1. Either way, the hot idle is lowish but ok and the cold idle pressure could come down, so that means a lower first number and the same or higher second number.

Bret

 

That's a good oil, as is the M1 Turbo Diesel 5w-40.

 

Argh. They can't order in 0W40 M1.

So my choices are 15W50, 5W50, or 10W30 in M1 synthetic.

 

Hot idle is always when you have the lowest pressure. 32 PSI hot idle pressure is plenty for any small block. They often run less than that. The old rule of thumb is 10 PSI per 1000 RPMs and that's still about right today.

I run 10W30 all the time in my motors assembled to typical specs and using a standard-volume pump (but often with a high pressure relief spring in the pump). If it can hold adequate oil pressure under all conditions, lighter oil always helps, as far as power production goes, not to mention it gets the oil where it counts faster on a cold start-up.

Thinner oil does have one downside, as far as I can see, other than whether you can hold pressure at temp or not..... your pump can suck the pan dry more easily at high RPMs, before you can get enough drain-back through the various internal engine passages. Remember the thinner the oil the more volume the pump has to push through the engine to hold any given pressure. A stock capacity pan with a high volume/high pressure pump and loose tolerances seems to be the combo you will see this problem first.

Crazy class-limited racers often run VERY light weight oil in their engines- way south of 30W. And they go through the traps with the oil pressure dropping down close to 0.

Many modern production engines are coming out with very light weight oils recommended for use in them- 0W20 weight becoming much more common these days. Friction reduction (fuel economy) is the primary concern here but they still have to survive the occasional WOT blast with wiping out bearings.

 

I question the conventional wisdom of "lighter oils get where they need too faster", seeing as these days I understand it being a positive displacement pump it moves volume despite restriction.

Some of us actually look at MEASURED results and while one 10w-30 might be just fine another like oh say the popular one can result in high iron wear. Not bad oil, in other applications it can work wonderfully. Point being MOST of what you will read about oil recommendations on these boars is flat out wrong. Most people rely on comercials and magazine ads for their "information".

Not saying thicker is better either just saying more indepth research and Used Oil Analysis is in order rather than just talking weights.

 

Thats odd.... Carquest has it ....Part # 44962 0w40 M1....

 

You can use Mobil 1 if you want, Another option is Shell ROTELLA T Synthetic 5W-40. We use it in road race bikes for endurance racing. you can get a gallon of this stuff at Walmart for $15.

Here is a good link regarding synthetics.

http://motorcycleinfo.calsci.com/Oils1.html

Its about motorcycle engines, but the info still applies. Not out to debate which oil is better, just giving you some info regarding oil choices.

 

I put in some Havoline 5W40 synthetic for now. The guy will order in 5W40 M1 in a few weeks.

 

You should try Amsoil 0w30, that's what I run in my 383.

Randy

 

I run Amsoil 5W-40 European Formula.