Using diesel rated motor oil in a motorcycle

I know this is a non TDI question, but here we go.
Yesterday I was talking to a motorcycle repair guy. He stated that he runs diesel oil in his bikes due to it being more durable. From what he was saying it appears that he is very knowledgeable about bikes. Any truths to this?

My take is that this is an old-school type who is using a non-synthetic 15W-40 diesel oil in an old large air-cooled V-twin (HD, etc.) engine. What he is really after is using a heavier oil with a better additive package. The more robust additive package might help the rings stay clean and tight and reduce oil consumption, common problem with old V-twins. Separate engine and tranny sumps so no problem there. A synthetic diesel oil would probably work just as well.

I would not use a diesel rated oil in any Jap or Euro bike. They rev too high and there might be problems with foaming, shifting, and the clutch. The big reason the best motorcyle oils do not have the latest API ratings is because they can cause clutch slippage. That common engine/tranny sump...

I just bought a new bike. Been lurking around at a couple motorcycle forums. So far, I see a lot of people running Rottella 5W40 "synthetic" in there bikes. I'll see if I can find a link for you.

Here's a link. I'm still trying to decifer if it is all factual or not.

http://motorcycleinfo.calsci.com/Oils1.html

Clutch slippage comes from energy conserving oils. Energy conserving is found mostly in the API SL oils. These oils will cause clutch slippage. My Suzuki DR650 owners manual specifically states using non-energy conserving oil. From what I understand so far, CI-4 diesel rated oils will not cause problems with clutch slippage.

For my Japanese sport bike, if the API rating is later than SG, there is an additional requirement that the oil conforms to JASO MA. But, a lot of people use the automotive version of Mobil 1, and don't report any problems.

Think you will find a lot of informed guys using Delvac1.

Some of the 15W-40 "Diesel" oils (Like Shell Rotella) are a "mixed fleet" oils for both gas and diesel motors and have quite good specs for both.

--Nate

oil

I have run rotella synthetic and non-synthetic in my r6 for close to 23000 miles and it's still running strong. I just switched to delvac 15w40 since it's a bit cheaper. I put the delvac in my ktm. I'll see how it works out. So far so good. I don't forsee any issues.

Mondog1 said:

I was talking to a motorcycle repair guy. He stated that he runs diesel oil in his bikes due to it being more durable.

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It should do no harm as long as it meets the requirements for the bike. Diesel oils tend to have additives to handle the additional soot which the bikes don't need. There is no reason to believe they would be "better" for a bike.

I think part of the reason is price. I went to a cycle dealer last night. 1 liter of Maxima 10W40 was $9.75. I don't know how great this oil is, but most of the oils in the cycle shops is pricey. Castrol and Valvoline dino MC oil is around $3.50 to $4.00 per liter. Must be the diesel oil is a good compromise between being able to get a synthetic with good protection and long life without having to spend $30 every oil change on 3 liters of oil.

A 'for real' group IV or group V synthetic diesel engine oil such as Mobil Delvac 1 (Shell Rotella synthetic is a actually a Group III mineral based oil) in motorcyles which specify a 10W-40 would work very well. The benefits of a diesel engine oil vs. a gasoline engine oil are a more robust additive package for both detergency and anti-wear. Additionally, with wet clutches, no concern of lubricity enhancement additization as the diesel engine formulations do not contain these.
I would not suggest the use of a diesel formulation for engines which require a 50W, such as most HD's, etc.
However, with motorcycle engine sump capacities of 3 quarts +/-, a slight increase in cost for using motorcycle specific formulated oils would seem to be minimal. It IS difficult to know just what is and is not a motorcycle formulation in that some unscrupulous manufacturers just re-label automotive oils with motorcycle and double the price. There ARE real, for real motorcycle specific oils that companies have spent mucho dollars to develop, and from my experience are worth every cent..
George Morrison, STLE CLS

NB67 said:

I think part of the reason is price. I went to a cycle dealer last night. 1 liter of Maxima 10W40 was $9.75. I don't know how great this oil is, but most of the oils in the cycle shops is pricey. Castrol and Valvoline dino MC oil is around $3.50 to $4.00 per liter. Must be the diesel oil is a good compromise between being able to get a synthetic with good protection and long life without having to spend $30 every oil change on 3 liters of oil.

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This white paper is the result of more than $300,000 in lab testing. https://www.amsoil.com/lit/g2156.pdf This info can be used to compare the HDEOs to the tested M/C oils, provided one can get the desired info for the HDEO.

One of the companies has PAO oil and synthetic filters that are guaranteed for double the manufacturer's change interval. This can put the price of the products well under the shelf price of HDEO - especially if one lives in an area with a longer riding season.

I run Heavy Duty Diesel oil in my Suzuki. Because the Dodge CTD holds 3 gallons I usually have a lot of it available. I did try some of my Amsoil HDD in the bike once but it made the clutch slip, but a couple of short interval drains using Shell Rotella let the clutch hook up again.

bulabula said:

I run Heavy Duty Diesel oil in my Suzuki. Because the Dodge CTD holds 3 gallons I usually have a lot of it available. I did try some of my Amsoil HDD in the bike once but it made the clutch slip, but a couple of short interval drains using Shell Rotella let the clutch hook up again.

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Have used Amsoil 20-50 non bike oil in all my bikes with and without wet clutches and never in 40+ years had a clutch slip. use it in my many ATA's also with wet clutches and never a problem. If you have a problem it is mechanical and the oil most likely cleaned the crud from the disks. You would have went back to a few changes of Amsoil it would also have been fine.

sootandclatter said:

Have used Amsoil 20-50 non bike oil in all my bikes with and without wet clutches and never in 40+ years had a clutch slip. use it in my many ATA's also with wet clutches and never a problem. If you have a problem it is mechanical and the oil most likely cleaned the crud from the disks. You would have went back to a few changes of Amsoil it would also have been fine.

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I believe you, but I'm telling you Amsoil AME slipped - eg no more wheelies until it was replaced. It was also evident on the GPS. There isn't any mechanical problem either. Many others have also documented it as well. Maybe these suzuki clutches are special, there are lots of varibles that could have an affect: number of disks, material of clutch disks, weight and horsepower of bike; adjustment of the clutch, clutch spring tension. AME could also very well be a different formulation than the 20-50 stuff you referred to.

Glad to hear you like it in your bike - I like it in the truck.

Chris - which oil did you use that slipped - the HDD (5W-30 heavy duty diesel) or AME (15W-40 HD Diesel)? Thanks!

This is anecdotal but I have read in a number of places that Delvac1 and Rotella T Synth are 2 VERY good options from testing and user experiences.

I'm running Delvac 1300 in my Honda CBR929. No problems.

AndyH said:

Chris - which oil did you use that slipped - the HDD (5W-30 heavy duty diesel) or AME (15W-40 HD Diesel)? Thanks!

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Andy, it was the AME.