Simplicity 7790 diesel motor oil?

[3416H 0]

Hello, I just picked up a 7790 diesel and i'm going to change the oil. I was going to use 5w40 mobil 1 synthetic diesel motor oil. Is that a acceptable oil for summer use? Any thoughts and opinions appreciated. Thanks, 3416H

[Zach 0]

I run 15w40 in my vw rabbit and the engine in that isnt much bigger than your 7790's engine.

[BLT 461]

Here is the recommendation right out of the operator's manual -4 deg F and below - SAE 5W -4 deg to 32 deg F - SAE 10W 32 def to 68 deg F - SAE 20W 68 deg and above F - SAE 40 Zach's VW was probably desinged around 15W40, the engine for the 7790 was not as 15W40 was not available 25years ago. 10W40 in Diesel engine industry was almost a complete disaster, I couldn't beleive 5W40 would be any better.

[Killer_A-C 0]

Be careful with the synthetic oil in older engines.Alot of times they will start leaking around the seals.JMO...

[3416H 0]

Thanks for the info so far. Does anyone have a 7790 that can tell me what they run, or have had good luck with? Thanks

[UCD 8]

I run Mobil 1 5w40 diesel oil in my 7790 year round for years and it has over 5000 hrs on it no problems

[3416H 0]

UCD, Is it synthetic oil also? Thanks

[427435 0]

I'm using the 5w-40 Mobil 1 in my 7790. No problems to date nor is there any reason to expect any. Good year around oil that I'll only need to change once per year.

[3416H 0]

Are you guys talking about the Mobil 1 synthetic diesel oil? or conventional? Thanks

[427435 0]

quote:

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Originally posted by 3416H
Are you guys talking about the Mobil 1 synthetic diesel oil? or conventional? Thanks

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All Mobil 1 oils are synthetic oils.

[3416H 0]

dOd Didn't even realize that, thanks for the help guys.

[427435 0]

quote:

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Originally posted by BLT
10W40 in Diesel engine industry was almost a complete disaster, I couldn't beleive 5W40 would be any better.

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Was the 10w-40 oil dino oil or synthetic oil??

[BLT 461]

quote:

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Originally posted by 427435

quote:

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Originally posted by BLT
10W40 in Diesel engine industry was almost a complete disaster, I couldn't beleive 5W40 would be any better.

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Was the 10w-40 oil dino oil or synthetic oil??

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Dino. Synthetic wasn't on the drawing boards in the mid 80's for our industry and there was a gray area about using it and getting warranty. The whole industry for the larger trucks seems to be on 15W 40. Most Diesel engines today were and are designed around it and have fared well. An engine today in class nine trucks will get about 600,000 miles or better life to rebuild under normal maintenance, 20,000 - 25,000 mile oil changes using dino and having oil analysed periodically. Engine people don't recommend any extended oil change intervals using synthetic, so there no cost advantage. Also, Diesel engines start better now in cold weather then they used to.

[427435 0]

The problem with wide viscosity range dino oils is that they start off with an oil of the low number (a 5 weight oil for a 5w-40) and then add lots of viscosity index improvers to keep the viscosity from falling too far as it warms up and be at a 40 weight viscosity at operating temp. These VI improvers shear down with use, however, and the the 40 weight at operating temp becomes a 30 weight and then a 20 weight as the oil is used. A good synthetic oil doesn't use many (if any) VI improvers and doesn't lose its operating temp rating as it is used. In other words a 5w-40 dino oil will likely become a 5w-20 oil before a normally scheduled oil change. A 5w-40 synthetic will still be a 5w-40 oil after extended use (or very close to it). The other issue with a wide range multi-viscosity dino oil is that after enough VI improvers are added to make it a wide range oil, there isn't much room left for other additives like detergent and acid neutralizers.