Diesel Owner - What oil to run in my gasser?

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Oct 10, 2002
I will start off by saying I am the owner of a Dodge Cummins that I am currently running Petro Canada Duron Synthetic 5w40 in, but I recently purchased a 1992 Pontiac Bonneville as a second vehicle. It will primarily be used as my "grocery getter" particularly in the winter months. I would like the car to last me for quite some time so I am trying to decide which oil would be my best option for the car. As I mentioned the car will primarily be driven on short trips averaging 2-6 miles. It will also be used as an my primary vehicle to respond to emergency calls. This means getting in the car in the middle of the night when the temps are in the single digits and driving it harder than a stone cold car should be drriven. What I am thinking, to keep things simple, is to run the Petro Canada 5w40 in the Bonneville. Although it is not a bad price, I think I would rather run less expensive oil. Also, this is just a personal feeling and I have no factual informaiton to back it up, but I think the 40 on the top end might be a little heavy. The other thing I am thinking is to run a dino 10w30, probably Chevron or Pennzoil as these seem to be some of the best dino oils available. I'm not really interested in running a 5w30 dino as the information on this site leads me to believe it will fall out of grade too quickly, but I will consider it if it is suggested to be my better option. If I run the dino, I'm thinking about 2,000 mile changes just due to the type of short trip driving the car will be accustomed to. What do you think would be my best alternative. I appreciate your help. Thanks!
Mobil 1! (inside joke) Any and all of the oils you listed will work fine. I like diesel-rated HDEOs like Rotella T Synth, if you have access to Petro Canada, go for [Big Grin] it.
A guy I used to know had a Volvo turbo (aftermarket, 18lbs boost). He used to do "extended drains", by changing the synthetic oil ealry in the volvo, and then putting that oil in his daily driver. Not sure on the sump capacities of the cummins, but you could change the oil on the new car maybe three times for a sump full of lightly stressed Cummins oil.
If you want to save a buck I'd go with with Chevron Supreme, Pennz seems to show great UOA's too but is a bit more money (at least here). As for grade, 5w30 winter 10w30 summer is a popular and logical choice in colder climates. For interval I would think 3000 miles would be plenty safe as this is the typical severe duty interval.
RC, Run the same Duron, 5w-40 ...it's an excellent gas engine oil for older cars. See the analysis posted from my 1990 Audi 100 in the UOA section. I think it was about 3-4 weeks ago. I'd recommend the Amsoil 10w-40 for this application and the PC Duron is the same type of product .... The level of sulphated ash in the Duron is only 1.35%, so there won't be any issues with combustion chamber deposits and the engine will stay nice and clean. I sell Amsoil, by the way, but there are many excellent oils out on todays market .... Tooslick Dixie Synthetics
Thanks for the suggestions. I'm not sure if I have made up my mind on which way to go. I have a couple additional questions that perhaps you can clear up for me. I'm certain the PC will offer the best cold weather protection for this application but is the 40w on the top end a little heavy? Or given that this car has 130k on it the 40 on the top end should actually be a little better (this is the assumption I have made form reading these forums). If I decide to go with a conventional oil, the infomation I have read here steers me away from a 5w30. It has a tendancy to shear down a little more and offer less protection in the higher RPM's than the 10w30, is this correct? But given the cold operating conditions and the fact this car will be driven hard when cold would the 10w30 still be a better choice. Not that I think about it I guess the additional cost of the PC is not that big of a deal. I keep forgetting I'm only changine 5 quarts of oil on this car, not 11 like the Cummins [Smile] Thanks again for all the help.
Tooslick, I took a look at your UOA posted. The numbers look great. I was surprised that at 10k miles the TBN had fallen to only 4 from 10.5. I would expect it to hold up better. Maybe a higher depletion of TBN is standard on a gas engine with a smaller sump capacity, I'm used to reading Diesel UOA's.
RC, Gas engines generate more oxidation and nitration than do diesel engines, so the TBN does drop faster. Gas engine also burn more fuel per mile, so the oil gets contaminated more quickly .... The Duron , 5w-40 provides excellent wear protection, that's the key piece of data out of that analysis .... Ted
Thanks Ted for the info on why the TBN is affected more by a gasser than a diesel.
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