Considering going to 5W-40 synthetic

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Pyrotechnic

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I have a small block chevy V8 which I have been running 15W-40 in since the day it was built, which was about 30K miles ago. It's a 383 and makes around 450HP. It's been doing great on the 15W-40 and I've only been putting around 3000-5000 miles a year on it.

Now that I've moved to a bigger city, the vehicle is driven daily and I'm also planning some trips to the drag strip. Would 5W-40 synthetic be worthwhile on the next change? I'm not interested in longer drain intervals. What I'm really looking for is better cold start up protection, increased fuel economy, and overall better protection against wear for the now tougher operating conditions.

This engine has a high volume racing pump as well. It does take quite a bit more power to turn than the stock pump. When priming the oil pump for the first startup with the same electric drill I've used to prime other small blocks with stock oil pumps, the drill was noticeably bogged down trying to turn the pump. All the engines primed with that drill had 15W-40 in them. I know this is rather unscientific but this racing pump does eat alot more power than a stock pump. Would the 5W-40 synthetic be easier to pump and free up some power? I'm also thinking less strain on the cam/distributor gear?
 
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Short answer: Yrs

The running viscosity is the same (40) but to get there, the starting viscosity will be much lower (5 vs 15)
 
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Is this a hyd roller?
If I assume YES (why WOULDNT anyone build a roller?!)
Regardless, Idun the "stock" pump that's been gone-over with the bypass spring your builder wants. BB pumps in SB chevys aren't usually warranted. Typical "HOT Rod mag reader" mistake You may want to try the dual rated (typ API SJ) motorcycle superbike oil (4T which is typ a 10w40 HP) or HDEO Rotella T6. I wouldn't try to run a ILSAC PCMO; they barely work on moderate specific output engines. I wouldn't run a wide multigrade dino, they are highly compromised and dirty.
 
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The 5w40 would be much easier on the oil pump drive and distributor drive gear when first starting the engine with cold oil. But I recommend going to a lighter 40-weight such as Pennzoil Ultra Euro 5w40 or Mobil 1 0w40. And of course, the 0w40 would be even easier on the pump drive than the 5w40.

How much oil pressure are you seeing on your gage when:
1) you first start it and idle
2) you rev it to ~3000 rpm with cold oil
3) you are cruising down the higway with the engine at operating temperature
4) you run the engine to maximum rpm
 
Why do anything except go straight to M1 0w40? FWIW, I run it in my two vintage big-blocks (still with non-roller cams, no less) and it turns in good numbers.

But given that you've got a roller cam and don't need quite as much AW additive,you could go to a good 5w30 or 0w30. With a HV oil pump, that really should be no problem.
 
Yes, the engine has a roller cam.

As far as the high volume pump, I installed it knowing they are generally frowned upon because they waste power. At the time of the build, Melling had redesigned their stock replacement pump and people were having issues with the pump casting breaking. Rather than take the risk, I bought a Melling Select series pump instead. I knew it would waste power but I figured the extra power wasn't worth it at the risk of catastrophic failure.

Cold start and idle - 65 PSI
Cold rev to 3000 RPM - 85 PSI
Hot cruise at 2400 RPM - 60 PSI
Max RPM - Didn't wanna get too squirrely on the way home from work tonight, I'll have to get back to you on that one.

My first thought was the Shell T6 5W-40 just because my engine takes 2 gallons, and it's readily available for $20 a gallon. It appears that Mobil 1 0W-40 is also available at Walmart for $25 per 5 quart jug, which works out to about the same price per quart. For some reason I had it in my head that the 0W oil would be really expensive. Since there is no difference in price, which one will offer the most wear protection? My first instinct would be the M1, just because it would be even easier to pump and would offer more cold start protection.
 
Those pressures are a bit high, but not insane. I was worried that you would be running 100 psi on the Cold rev to 3000, and 80 psi during hot cruise at 2400. 10 psi less wouldn't hurt anything and a lower viscosity oil would be a step in that direction.

Comparing viscosities between RT6 and M1 0w40:

____40C 100C
RT6 87 14.2
M1 75 13.5

M1 is lower viscosity.
 
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Isn't 10w-30 the recommended viscosity for your application?

I'll be the sole dissenter here -- you've stated that you're not interested in longer drain intervals, and there's no compelling reason otherwise to invest in/run synthetics.

Quaker State Defy 10w-30 with a Fram Tough Guard filter would be entirely appropriate, and available from Walmart at low cost.
 
Thanks everyone.

I just finished reading all 10 pages of this: http://www.bobistheoilguy.com/motor-oil-101/. Seems like everything I ever thought about oil is wrong!

It looks like I could run a 0W-30 oil given the oil pump I have. That may even be more appropriate than the 0W-40. The dino 15W-40 was chosen in the first place simply because I felt it was the closest thing to racing oil without getting into the $5+ a quart prices. I am not so concerned about price now, but it still needs to be somewhat cost effective given the 2 gallon capacity. Mobil 1 0W-40 is very readily available and would be an improvement over what I am running now. It seems Mobil 1 doesn't offer their standard synthetic in 0W-30?
 
Mobil's 0w30 does not have the same kind of additive pack that their 0w40 has, and is a light fuel economy oil. A 0w30 you could consider is Castrol Syntec European Car Formula. We call it German Castrol (GC) on this board because it has a note on the back of the bottle that says Made in Germany.

But in terms of viscosity, German Castrol has about 8% lower viscosity than M1 0w40. It is about as heavy a 30-weight oil as you can find. It's only about 3% below the limit for being a 40-weight.

viscosity @ 40C: 72
viscosity @ 100C: 12.2
 
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Given the limited use of the car, I'd want to know if a 15W40 will protect better against corrosion than a 0W30, in regards to long periods of inactivity.
 
Originally Posted By: Pyrotechnic
Thanks everyone.

I just finished reading all 10 pages of this: http://www.bobistheoilguy.com/motor-oil-101/. Seems like everything I ever thought about oil is wrong!

It looks like I could run a 0W-30 oil given the oil pump I have. That may even be more appropriate than the 0W-40. The dino 15W-40 was chosen in the first place simply because I felt it was the closest thing to racing oil without getting into the $5+ a quart prices. I am not so concerned about price now, but it still needs to be somewhat cost effective given the 2 gallon capacity. Mobil 1 0W-40 is very readily available and would be an improvement over what I am running now. It seems Mobil 1 doesn't offer their standard synthetic in 0W-30?


If you had a 0w30 that had the same kind of additive pack as M1 0w40, you'd be fine. Heck, you'd be fine even if this were a commuter car with a roller cam, but since you do say you plan to run it at the track also, I'd go for the stronger additive package in M1 0w40. To get that in a 0w30 or even a 5w30 or 10w30, you pretty much have to go to boutique oils like Redline, Amsoil, etc. which will be considerably more expensive. I think M1 0w40 is your best overall pick.
 
If you are not the engine builder--then what did the builder recommend? I am guessing 15W-40. In my view, the only reason to change to a synthetic 5W-40 would be to compensate for cold starts in cold weather. I am assuming, looking at your oil psi readings, that the engine does not run hot, so no justification there for synthetic. Finally, once the engine oil is at operating temperature, there should be little difference in oil "drag" on the engine between one 40-grade oil over another. So my vote is to consider keeping what you use now. If you do decide to go to 5W-40, I'd recommend any one of the name-brand HDEOs.
 
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