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B43G. . . 318 burning oil. . . Sea foam or 15W-40, or?????

3279 Views 7 Replies 4 Participants Last post by  ducks13
My starter went out a couple weeks ago so I drained the oil, pulled the motor, replaced the starter.

I replaced the vavoline straight weight 30 oil with 15W-40 vavoline oil. I also put in some SEA FOAM in the gas tank only.

I ran the tank and it smoked like I thought it would from reading other posts on this website.

I have now put on about 5 hours of mowing and notice that I get what looks like white, but must blue smoke periodically while mowing.

Motor runs strong with no misses, etc.

I have had to add just over one QUART of oil in around 5 hours! I never had to do this with the 30 weight oil, so what gives?

Should I not be running the 15W-40 oil? I read on hear where some have said that using this oil helped stopped using oil?

Thanks in advance for the advice!

My motor has around 460 hours on it and I adjusted the valves recently. Goodness, thinking outloud, I hope I didn't miss adjust the valves!

I know I triple checked the valves so I don't really suspect that is the issue.

Just confused since I used the SEA FOAM and the 15W-40 for the first time, at the same time. . .
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How much Seafoam did you use? Adding only to the fuel is only 1 ounce to 1 gallon, 318 has a 5 gallon tank = 5 ounces.

When you adjusted valves did you re-install the reed valve, flat washer & spring correctly?

Onan manual states if installed incorrectly can cause oil leaks, high oil consumption, rough idle, etc.

Order of assembly is bottom to top:
Breather Baffle
Reed Valve
Flat Washer

For your oil choice, summer temperatures I would be using a minimum of 30W HD oil.

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I would expect it to use more oil when using hte 15-40. Go back to the 30wt.

I believe the Seafoam can make the exhaust smoke white.

Oil burning should show up as a puff of blue smoke when the engine is under a load such as when engaging hte PTO or going up a steep hill or mowing tall grass.
I def. used more than 5 oz of sea foam. As far as reinstalling the aforementioned parts, I am highly confident that I did as I took pictures of everything as I took it apart and also referenced the manual upon reassmbly.

Why would 15-40 smoke more than straight 30 weight?

Should I go to straight 40 weight since I only run the mower during the warmer months?

Using over 1 qt of oil in 5 hours I would expect to see oil smoke constantly. I would start with the basics, bring engine to operating temperature and do a dry and wet compression test.(Post results)

The oil control rings should compensate for the different weight oil and I would switch back to 30W HD oil.

Thanks Bob for the advice. I miswrote and/or misspoke.

I am using just over one PINT of oil every 5 hours or so.

I am use to the dipstick on my automobiles.

Regardless I am going to see if I can borrow a tester to check compression per your suggestion.

1 pint is still a lot. Definately more than normal.

No offense, but I believe the SeaFoam quantity is correct but not entirely. This is from the SeaFoam tech info on their website. On the can it actually doesn't list a maximum quantity, IIRC it just says more for bigger problems. The website says you can run it at up to a 50% mix.
Type of Fuel
Normal gasoline grades (including 10% and 15% ethanol blends)

Recommended Average Mixture
1 oz. Sea Foam Motor Treatment per gallon of gasoline

Can mix up to 2 oz. per gallon of gasoline if necessary. Mixing at less than 2/3 oz. per gallon will impair
I am not sure why multi-vis oil gets burned easier but it has been my experience with several different engines including my 318.
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