18HP,TWIN CYLINDER ONAN MOTOR. 1976 MODEL, OIL CH

OIL ADDITIVE OF ANY BENIFIT TO BE ADDED WHEN CHANGING OIL IN THIS UNIT. IF SO--WHAT TYPE OR BRAND

THE BEST WAY TO MAKE THIS OLD BABY LIVE IS TO USE ONLY DIESEL 15/40 OIL, BRAND OF YOUR CHOICE I ALWAYS USE 1/2 BLUE BOTTLE OF STP. DON'T EVER LET OIL LEVEL RUN LOW, IF SO IT WON'T BE VERY PRETTY, MOST ALL ONANS USE SOME OIL, SO CHECK OFTEN, IF THE ONAN HAS A OIL FILTER CHANGE OFTEN, BOUGHT A SEARS SUBURBAN 5 YEARS AGO TO RESTORE UPON TEAR DOWN FOUND OIL FILTER TO BE ORIGINAL WITH SOME FACTORY PAINT BUT OIL PLUG WAS WORN TO A NUB, THE SMALL PLATE COWERING THE OIL FILTER HAD NEVER BEEN REMOVED, THE OLD ENGINE TURNED OUT VERY WELL, PROBABLY 2000 HRS. ROUGH USE. DO NOT USE AUTO OIL. EXPLAINING WHY IS ANOTHER STORY

I have a 1978 GT18 and have been using a straight 30w during the summers and a little lighter weight as per the information shown on the lid of the air cleaner. Did not know that to use a diesel 15/40 oil. Am I still okay?

Midnight77

Hi
The best advise you will get is in above post, If you use modern day auto oil you will possibly loose the cam shaft lobes.
Jimmy