# Question about oil for a diesel tractor and a gas tractor



## Randall Lyons (Dec 11, 2019)

I'm not a mechanic, so oil is oil to me. I have owned 3 diesel tractors and now have a gas MF35. My question is I need to change the oil and I have about 6 qts of Rotella in my shop that is for diesel tractors. Can I also use that in my gas tractor? It is 4 qts of 30 wt. and 2 qts of 5W40. See any problem in mixing them since it's just an old 1960's tractor?


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## pogobill (Jan 31, 2012)

If the Rotella has an "S" specification, I think it would be alright. ie: API SN or SM. I understand that diesel engine oil is thicker than gas engine oil, so It may cause the tractor to run a little hotter.
There are a few oil guru's here that may be able to give you some specifics.


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## Bob Driver (Nov 1, 2017)

Randall Lyons said:


> I'm not a mechanic, so oil is oil to me. I have owned 3 diesel tractors and now have a gas MF35. My question is I need to change the oil and I have about 6 qts of Rotella in my shop that is for diesel tractors. Can I also use that in my gas tractor? It is 4 qts of 30 wt. and 2 qts of 5W40. See any problem in mixing them since it's just an old 1960's tractor?


Welcome to the forum Randall. Don't know how much time you've spent on these type of forums, but if you want to get something going right off the bat, asking a question about oil, or tires is a sure way to do it.....

It's like asking a bunch of divorced guys which women are crazier blondes, brunettes, or redheads. *Everybody* has got a story and they're all based on how long it took them to blow up and how much it eventually cost....

With that thought in mind, my only suggestion is going be stay away from the really expensive ones (even if the package looks really good) and think about how you're going to eventually have to get rid of a messy problem

P.S. Don't even think about "mixing them", they really don't like that and you could end up with your stuff on fire....


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## Randall Lyons (Dec 11, 2019)

Randall Lyons said:


> I'm not a mechanic, so oil is oil to me. I have owned 3 diesel tractors and now have a gas MF35. My question is I need to change the oil and I have about 6 qts of Rotella in my shop that is for diesel tractors. Can I also use that in my gas tractor? It is 4 qts of 30 wt. and 2 qts of 5W40. See any problem in mixing them since it's just an old 1960's tractor?


UPDATE: I DID change the oil last Dec and mixed it. That may or may not have contributed to my current problem - I dunno.

It is now May 2020 and I've bush hogged with my tractor twice. Both times, my oil pressure starts off at 40 psi and as it warms up, it starts dropping. I figure it should stop dropping around 15-20 psi, but it dropped all the way to 5 psi, so I shut it down and parked it.

Is 5 psi normal or do I have a problem?


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## Chris3510 (May 3, 2020)

Run a solid 15w40 in that old tractor. It’ll be fine. Rotella,Delvac1300, Delo400. All are good, but I wouldn’t mix them. Pressure may drop due to viscosity, deterioration, or loose tolerances in main bearing.


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## Randall Lyons (Dec 11, 2019)

Chris3510 said:


> Run a solid 15w40 in that old tractor. It’ll be fine. Rotella,Delvac1300, Delo400. All are good, but I wouldn’t mix them. Pressure may drop due to viscosity, deterioration, or loose tolerances in main bearing.


OK, I'll change the oil again and put ONLY 15W40 in it and report back. Thanks!


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## Scottp1951 (Jun 13, 2020)

Low oil pressure at warm idle. Buy a good oil pressure tester. OTC has one on Amazon for about $63.99. Others are priced from $22 on up. Check your pressure with the good tester and compare it to your gauge.


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## Ed Williams (Jun 13, 2019)

Mixing oils is a very bad idea. Slight variations in oil formulas can result in massive sludge deposits that are a PIA to overcome.

In a former life, 50+ years ago, I bought a Ford Bronco with 300 motor. Like all new stuff, first project was oil and filter change. There is always some risidual oil left in the motor. I used my usual oil, Quaker State, without any questions. Within 500 miles I was having motor issues, sluggish running, oil smoke out of the tail pipe, oil consumption, oil pressure, etc,etc. I removed the valve cover and it was complete filled with gooy sludge. I wound up having to pull the motor, completely dissassemble, send all parts to a speciality cleaning shop with huge hot solvent circulating cleaning baths. After cleaning, did a complete motor overhaul. Cost wise, I might have been better off purchasing a complete new engine including head. Finally got everything done and running again, but my "bargin" find was no longer a bargin. I don't know what oil had been used originally, but it was certainly not compatable with the PA Crude oil I used.


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