I have a '69 318 that used to run on 10w30 Mobil 1 Synthetic oil for several years. I could drive the car all summer long (about 500-600 miles) and the oil level stayed at the FULL mark. I changed to Joe Gibbs Driven HR-10w30 Conventional oil along with a fresh oil filter. Added 5 qts. oil and ran it about 10 miles, parked it and checked the oil level about a week later. It was on the ADD mark (1 qt. low). Where in the world did that 1 quart of oil go? (Did not go into the water system, nor on the ground and did not show in the exhaust).

Sounds like your 318 isn't a Joe Gibbs fan.

Some engines for whatever reason will not tolerate changing the oil menu. I've had a couple that just guzzled oil after changing brands but went back to normal after changing to something else.

I'd put it back on it's old diet and see what happens.

Kevin

IMO if it burnt a quart of oil in about 10 miles it would have had thick smoke cloud unless it leaked out. Add a quart and see what happens. Are you sure that it doesn't have a 6 quart system. Some trucks did back in the day.

It's always taken 5 qt. with filter change ('69 Satellite). Started again in the shop and let idle for awhile and the exhaust was clear, no smoke whatsoever. I'm going to add the 1 quart, but will be awhile before I can drive it due to the salt on the roads.

The van loves mobil 1, don't think I ever need to top it off between its yearly oil changes. As much as it seeps out from I think every possible sealing surface its never 'low'. Tried some dino 15-40 rotella and that crap ran right out like water and I topped it off w/mobil 1 until I think the rotella was totally purged and all was good again Of course the mobil 1 is 15-50