first oil change on 5500 onan gas generator

[roadglide]

I ordered 2 onan filters. My question I use 1300 mobil 15/40 diesel oil for the Duramax. The subject has been beat to death in other threads. I rarely get above 100 degrees. I know what is recommended but at $12 a quart ordering its not right. 15/40 0il is really hard to find for gas engines in my area. I would like to know a good alternative oil.

[PerryB]

Any quality 15-40 such as Delo or Rotella is fine. Theyre aimed at the diesel market but are also excellent choices for anything that calls for that viscosity range. Automotive grade 10-40 would also be fine. Synthetic would be a complete waste of money in this application.

[roadglide]

Thank you I have read where 15/40 rotella is used more often, straight 30 weight isn't a bad choice and understanding oil viscosity is mind boggling. I guess it has to do with weather condition.

[DiverB]

My last toy hauler had an Onan 4000 generator and I put just about 300hrs on her and I ran Amsoil straight 30 and never had any problems and I also had the oil analyzed at 100hr and 200hrs. Most of my time on the old generator was at the sand dunes in CA & AZ and I also use to camp up in Cloudcroft, NM and the straight 30 was just fine for either temperature.

I'm running the same oil and oil filter (K&N HP-8029) in my new Onan generator. I think the Onan is the best generator out there in my opinion. Most of my camping is always dry so I use the generator a lot!

[old timer]

I am a firm believer in full synthetic oil in all my stuff lawn mower too. It's especially beneficial in something that may get hot and not much air flow over the motor. It doesn't brake down like conventional oil. It lubricates better. Its great for engine seals. I have no idea why they sell a blend. They don't even tell you how much synthetic oil they blend. It could be only 1%. It may be more expensive but it's worth it in the end. I have a Chrysler Cirrus that has 278,000 miles and it doesn't use or drip oil. I have only used Mobil One in it. I drive it like I stole it. Commute car.

[roadglide]

I used 30 W Castro because that was all I could find . It seem like 15/40 for gas engines and 30 W is the thing of the past. Ill be ready for the next oil change with a synthetic 30 W .

[gearhead]

Shell synthetic Rotella 5w-40 should work well. I run it in our Generac 20k watt whole house back up generator.
Most wear will be at start up with any oil but particularly a straight 30. Conventional oil multi grade will have Viscosity Index Improvers that can wear/shear. That is where synthetics shine...they have no VII to break down.

[gearhead]

From Chapter 3 of Motor Oil 101.
http://www.bobistheoilguy.com/motor-oil-103/

A main advantage that the synthetic has over the mineral based oil is the ability to lubricate at startup. Both types of oil have the same specifications at 104°F, 212°F and 302°F. It is the startup viscosity characteristics that separate these oils. Synthetic oils do not thicken as much on cooling. They have better fluidity as the temperature drops.

A synthetic oil that is labeled as 10W-30 is less honey like as a mineral based 10W-30 motor oil at startup. They both have a thickness of 10 at normal operating temperatures. At 75°F the synthetic is not as thick. At 32°F the difference between the two is even greater. At 0°F the mineral oil is useless yet the synthetic works fairly well. Just keep the RPM to a minimum.

[kilolima]

I am a firm believer in full synthetic oil in all my stuff lawn mower too. It's especially beneficial in something that may get hot and not much air flow over the motor. It doesn't brake down like conventional oil. It lubricates better. Its great for engine seals. I have no idea why they sell a blend. They don't even tell you how much synthetic oil they blend. It could be only 1%. It may be more expensive but it's worth it in the end. I have a Chrysler Cirrus that has 278,000 miles and it doesn't use or drip oil. I have only used Mobil One in it. I drive it like I stole it. Commute car.

what he said. Some new autos are 20,000 between oil changes. My Audi was 10,000... full synthetic. Saves time, money, footprint, worry, to name a few.

[PARAPTOR]

Has anyone heard of PRO-Select Premium SAE 10W30 4 CYCLE ENGINE OIL SOLD AT LOWES. After reading these posts and just about due for an oil change on the ONAN, some thought I should use this product especially designed for 4 cycle air cooled engines. Anyone have any experience/comments on this product as well applicability to the Onan generator. (tx)