10w30 or 0w40 synthetic oil for Gen 2?

[VIPER GTSR 91]

The factory specifies 10w30 for Gen 2 but when these cars were built I dont believe 0w40 was even out. The factory fill for newer Vipers and Vettes is 0w40 which I think is great. My question is: Dont you think 0w40 gives a better viscosity and heat range for the Gen 2 also? I would like to ask this question to the Conner plant guys but may take too long for their answer. Your thoughts...

[belair1957]

Try e-mailing Royal Purple. I sent them a question on diff and trans fluids. They responded within a couple of hours.

[VIPER GTSR 91]

Originally Posted by belair1957

Try e-mailing Royal Purple. I sent them a question on diff and trans fluids. They responded within a couple of hours.

Good idea and will do so, but how familiar are they with the Gen 2 Viper engine specifically?

[VIPER GTSR 91]

Wizard, Jon B., Woodhouse, Archer, chime in here!!!

[chimazo]

I've read that auto manufacturers redesigned their engines for tighter clearances and instituted precision machining techniques that take advantage of thinner oil to deliver improved fuel economy through reduced friction. One of the car magazines tested various oils and found that lighter weight oil made more HP, and lighter synthetic oil made even more on top of that, but both lighter weight-ranges made less oil pressure. The synthetic manufacturers argue that the lower pressure is irrelevant due to their products' higher shear strength.

Personally, I wouldn't use "0w" anything on a higher mileage car.
Additionally, since the forged piston GEN2 motors would have higher bore clearances to account for expansion vs the '00-'02's cast pistons who's reduced thermal expansion rate allows the piston to be run with reduced clearance and produce a better ring seal, I wouldn't use "0w" in these (forged) either. Just my thoughts...

[Tom, F&L GoR]

An SAE 0W-40 would be better.

The "0W" label only means something at very low temperatures; in this case that the oil allows good engine cranking speeds down to -35C and good oil flow through the oil pickup tube at -40C. It means nothing as far as warmed up temperature operation.

The "40" means it is thicker than a "30" when at the warmed up oil sump temperature. However, there is "fluid friction" and so an SAE 40 will have slightly more drag in the bearings than an SAE 30. What the OEMs have done with better precision manufacturing equipment is to make surfaces more uniform, which lets them make clearances overall tighter, and then allows the use of oils with less fluid friction, like the oil designated for the 5.7L HEMI engine - an SAE 0W-20.

Pressure is not relevant other than indicating the energy needed to place the oil where it is needed. The general "10 psi for every 1000 RPM" comes from having to push the oil against the centrifugal force inside the crank so that it reaches the next crank throw. Once the oil is positioned ahead of a spinning journal, it will get pulled in anyway. The 60 psi out of the pump is not going to make much difference to the 10,000 psi pressure under the journal.

An SAE 0W-40 will therefore allow better starting, better fuel economy when warming up, and slightly poorer fuel economy when fully warmed, but with a thicker oil film - meaning directionally better engine protection.

OEMs did have the choice of an SAE 5W-40 in the past, a viscosity grade favored by the Europeans. Now that SAE 0W-40 is available, it will also be formulated for Euro applications, meaning it will have more additive than typical SAE 10W-30 oils. That alone is worth the switch.

[VIPER GTSR 91]

WOW Tom, that was some explanation and very detailed. Thanks.

[Steve 00RT/10]

Originally Posted by Tom, F&L GoR

An SAE 0W-40 would be better.

The "0W" label only means something at very low temperatures; in this case that the oil allows good engine cranking speeds down to -35C and good oil flow through the oil pickup tube at -40C. It means nothing as far as warmed up temperature operation.

The "40" means it is thicker than a "30" when at the warmed up oil sump temperature. However, there is "fluid friction" and so an SAE 40 will have slightly more drag in the bearings than an SAE 30. What the OEMs have done with better precision manufacturing equipment is to make surfaces more uniform, which lets them make clearances overall tighter, and then allows the use of oils with less fluid friction, like the oil designated for the 5.7L HEMI engine - an SAE 0W-20.

Pressure is not relevant other than indicating the energy needed to place the oil where it is needed. The general "10 psi for every 1000 RPM" comes from having to push the oil against the centrifugal force inside the crank so that it reaches the next crank throw. Once the oil is positioned ahead of a spinning journal, it will get pulled in anyway. The 60 psi out of the pump is not going to make much difference to the 10,000 psi pressure under the journal.

An SAE 0W-40 will therefore allow better starting, better fuel economy when warming up, and slightly poorer fuel economy when fully warmed, but with a thicker oil film - meaning directionally better engine protection.

OEMs did have the choice of an SAE 5W-40 in the past, a viscosity grade favored by the Europeans. Now that SAE 0W-40 is available, it will also be formulated for Euro applications, meaning it will have more additive than typical SAE 10W-30 oils. That alone is worth the switch.

Tom,

According to my 'sources,' the 0W-30 I use has a very similar additive package to the 5W-40 European oil they offer. One exception being a little more calcium in the 0W-30 for detergent. Both these oils would work well for me -- with a little higher film strength in the 40 weight product.

Steve

[98viperGTS]

Hey Tom, How can you tell if a oil has the additives like the European oils?

[VIPER GTSR 91]

Originally Posted by belair1957

Try e-mailing Royal Purple. I sent them a question on diff and trans fluids. They responded within a couple of hours.

Hey Tom and others, I got a reply back from RP and the rep. says he recommends RP xpr 5w30 for the Viper. (sales 101 of course). He thought the oil cooler on the new Vipers might be smaller than the Gen 2 and requires the 0w40???? After looking up the info on RP xpr 5w30, it states its for high performance engines, bracket racing, etc. but good for a daily driver also. Its very expensive at $13.00 a quart. Any thoughts on RP over Mobil 1 and does anyone use this brand and weight?

[Viper Specialty]

We always recomend the 0W-40 for all the previous cars, its a more stabil oil all around.

If only it wasnt so hard to find in decent quantity!

[belair1957]

Originally Posted by VIPER GTSR 91

Its very expensive at $13.00 a quart.

Cheaper at Autozone $7.29/qt and probably other parts stores.

[chimazo]

Thanks for the informative post (as usual), Tom!

With regard to RP, you can typically find it at Pep Boys, or order it online. I used it in my blown Z06 and just put it in my Viper, though I used old school 10w40.

[Tom, F&L GoR]

Originally Posted by Steve 00RT/10

Tom,

According to my 'sources,' the 0W-30 I use has a very similar additive package to the 5W-40 European oil they offer. One exception being a little more calcium in the 0W-30 for detergent. Both these oils would work well for me -- with a little higher film strength in the 40 weight product.

Steve

Steve, yes, the selection of the additive package is independent of the viscosity (as I know you know.) Either oil will work fine, I was trying to point out the differences.

"Film strength" is an interesting concept and I see many references to it. However, I don't believe it is part of any standard SAE category or that there is an ASTM test for lubricants to measure it. There is high temperature/high shear viscosity measurement (ASTM D4683, CEC L-36-A-90 (ASTM D4741) or D5481) in which an SAE 30 could possibly have a higher value than an SAE 40...

[Tom, F&L GoR]

Originally Posted by 98viperGTS

Hey Tom, How can you tell if a oil has the additives like the European oils?

At a minimum, the back of the bottle will make claims for ACEA performance in addition to the API category. They may also claim BMW, Daimler, Opel, Porsche, VW approvals.