10w30 SP in a Cummins
- Thread starter cneal
- Start date
Short-term, nothing. But you'd be foolish to keep it that way IMO. That's not a diesel rated oil and towing really isn't the issue.
I can't think of a valid reason why it should remain in there any longer.
I can't think of a valid reason why it should remain in there any longer.
Tell him that without the extra detergents and dispersants in the diesel oil, he will eventually see a nice layer of soot built up on the inside of his engine. The ring pack will also become sticky and his engine will start using oil and the power will decrease.
Never ever run a gas engine oil that does not have the appropriate ratings in a diesel.
Never ever run a gas engine oil that does not have the appropriate ratings in a diesel.
Were there signs that he shouldn't marry your daughter before this?
Delvac 1300 is 10w-30 and SP rated so it was probably that. If he used the 5 quart silver jug of 10w-30 then I'd drain it out soon but it's not gonna blow though pcmo 10w-30 is FA-4 in terms of hths and i never liked 10w-30 being recommended for diesels because people might put 10w-30 FA-4 by accident and have an oil that's too thin.
Also ram is silly for saying you can use 10w-30 but not 15w-40 and instead have to use 5w-40. But 10w-30 and 15w-40 can be made in conventional and syn blends and from the pds's i've seen when noack is avaiable the 15w-40 always has a lower noack and higher flash point even on cheap conventional and syn blends. The problems come from their new valvetrain not the oil. Higher noack and more volatile 10w-30 would cause more problems than 15w-40 if the oil was the issue.
Also ram is silly for saying you can use 10w-30 but not 15w-40 and instead have to use 5w-40. But 10w-30 and 15w-40 can be made in conventional and syn blends and from the pds's i've seen when noack is avaiable the 15w-40 always has a lower noack and higher flash point even on cheap conventional and syn blends. The problems come from their new valvetrain not the oil. Higher noack and more volatile 10w-30 would cause more problems than 15w-40 if the oil was the issue.
CleanSump
Site Donor 2026
CK-4 according to the owners manual. Mobil Delvac if he prefers Mobil.Well….which Mobil 1 oil exactly? Maybe check the jugs to verify if it’s appropriately Diesel rated, as lotsa diesel oils also have a gas rating
From wear to early oil change needed. Dump it & get CK-4 10w-30. That is if you're talking about a non "C" rated oil, right?
FWIW, Mobil Delvac 1 ESP 5w-40 is the best oil that can go in that motor unless he's motivated to use Delo ADF600. He wasn't far off the mark.
$110 buckets at Rural King but he just missed the $40 rebate cycle. (TSC will pricematch if no RK is nearby.) Rebates will probably come back in the fall.
$110 buckets at Rural King but he just missed the $40 rebate cycle. (TSC will pricematch if no RK is nearby.) Rebates will probably come back in the fall.
- Joined
- Mar 4, 2026
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- 182
The problem is going to be oil change interval. The HTHS os Delvac ESP 5W40 is only 3.8 it is the soot handling and ring pack cleanliness that will be the urgent concern. Depending on how low the AW additive package is it could blow through the detergents, dispersents and AW additives in 2000 miles or less or it could be just fine the problem is one of "You cant know what you don't know!". Keep in mind it is not just the additives that show up on a UOA/VOA.
Given how expensive a short block or long block 6.7 is to replace why chance it over an oil change accident? I am not one to fear monger or one to motivate out of fear but the risk to reward ratio in this situation is to great to roll the dice of chance. So I would recommend you drain the oil and refill with something that is proven for application.
It is fine to leave the oil filter in place and reuse it since it has next to zero time on it.
If you clean around the drain hole really well and get a clean 5 gallon pickle buck with lid and clean it out well you could easily reuse this oil in lawn mowers, older cars, general purpose lubricant, put it in cars and trucks etc....It does not need to be a total loss.
Given how expensive a short block or long block 6.7 is to replace why chance it over an oil change accident? I am not one to fear monger or one to motivate out of fear but the risk to reward ratio in this situation is to great to roll the dice of chance. So I would recommend you drain the oil and refill with something that is proven for application.
It is fine to leave the oil filter in place and reuse it since it has next to zero time on it.
If you clean around the drain hole really well and get a clean 5 gallon pickle buck with lid and clean it out well you could easily reuse this oil in lawn mowers, older cars, general purpose lubricant, put it in cars and trucks etc....It does not need to be a total loss.
I thought the new pickup truck diesels were designed more for 30wt oil. Ill have to look at the ones at work.
Main difference between SP, SM, SQ gasoline oil vs C oils like CK uses lots more detergent.
Probably want to change it before the oil starts to black out.
Ill run 10w-30 S rated oil in 6.7L Cummins. Have some customers that want absolutely sure their backup generators will start below 0F. Told them that's going to cost more, new batteries and thinner oil.
I requested 10w-30 diesel rated oil be ordered, they bought the cheapest 10w-30 they could find, which happed to be gasser oil. I let it run for 50 to 100hrs then change it.