Two separate things, please.

-Wife brought home oil made for high-mileage cars, first I've heard of it. Any opinions on whether this is worth it, a marketing gimmick, any downside? Her car has posted 3-4 more mpg for unknown reason. Changed air filter and cleaned AMM as well as oil change.

-Her car starts right up then stalls, once, twice or three times. Then runs fine and does not stall at lights. Stall happens when engine is cold or warm. But it does it some days, not others. Seems tied to humidity and/or warm weather. Thanks in advance.

Our significant others think alike! :-)

My girlfriend brought home two five quart jugs of Penzoil "high-mileage" oil for cars with over 75,000 miles. I went off on my typical curmudgeon explanation as to why our Volvo's don't really have "high-mileage" at 130k and 290k miles. Supposedly high mileage oil swells seals... which raised an eyebrow since the 240 has brand new ones. But whatever. I used it. Next time I won't. Life goes on. Mostly I was bummed because she brought home five quart jugs, which I despise... since I'm a clumsy pourer, I now have two extra quarts of oil without a home, and since one container isn't empty, I can't put the used oil in it.

-Ryan
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Athens, Ohio
1990 245 DL 130k M47, E-codes
1991 745 GL 280k (Girlfriend-mobile)
Buckeye Volvo Club

Does your car have a turbo?

Thank you all. I'll try the stalling fixes and report back.

If the high miles oil is a gimmick, as I suspected, I'll go without. I don't usually believe in magic auto fixes out of a bottle, but after an epiphany with miracle AMM cleaner recently, I thought maybe there was something to it after all.

If using high mileage oil helps you sleep better at night go for it. It's certainly not gone to hurt but your engine doesn't really need it. Bottom line if it makes your wife happy then do it. It's alot easier than trying to explain oil viscosity idexes, additives and engine wear rates. But it probably is just a marketing gimmick. Hard starting could be a gummed up idle air valve. Not too hard to remove and clean out with some carb or brake cleaner. Maybe remove and clean the throttle body also while you're at it.

if you cleaned the AMMthat would be my first guess on the stalling. I had a bum AMM that acted the same way , and it was a fresh rebuilt unit, put a new one in, not more problem.
Have you checked the error codes for fuel and ignition sockets 2 and 6 ( http://www.brickboard.com/FAQ/700-900/EngineOBDCodes.htm )
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-------Robert, '93 940t, '90 240 wagon, '84 240 diesel (she's sick) , '80 245 diesel, '86 740 GLE turbo diesel, '92 Ford F350 diesel dually

"High Mileage" oil is 90% likely to be marketing rather than engineering. Everyone's looking for that little sales edge. There may be tiny adjustments in the additive mix, but I doubt that you would see any real world difference in performance or durability. Giving these Red Blocks half-decent routine maintenance usually results in the engine outlasting the rest of the car.

Your increased fuel mileage is probably due to the clean air filter. Used oil at high mileages can actually thicken up, so an oil change can result in a bit less internal engine friction, giving a slight gain in efficiency.

I'd guess that intermittent stalling shortly after startup relates to a "lazy" Idle Air Motor/valve...others report improvement after cleaning this out...see archives.
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Bob (son's 81-244GL B21F/M46, dtr's 83-244DL B23F/M46, my 94-944 B230FD and 89 745 (LT-1 V8); hobbycar 77 MGB, and a few old motorcycles)