1998 V70xc, Just started to miss and skip,

[E Showell]

Robert -- I drove mine like a grandmother to maximize fuel mileage, but the valve's final curtain came on an 85 mph highway run.

I was also running regular gas for a while and I've been using Mobil 1 high mileage 10w30 and I am wondering whether the special additives they add to preserve seals might actually weaken them. I am curious how many who have suffered burnt valves were using Mobil 1 high mileage? Now I won't use fuel with an octane rating lower than 89.

My specific failure theory has to do with a front 02 sensor that was not replaced at 100K miles as part of regular maintenance, was in a slow death spiral but did not fail quickly enough to throw a code. My theory, again unproven, is that the mixture was being increasingly leaned out by the failing 02 sensor (I was getting great gas mileage --high 20s, like 28 mpg or so in stop and go traffic) and that it finally leaned so much that the valve burned.

[pred]

My wife drove it nice as well as when my sister owned it,
I drive my cars pretty hard, I like to see redline once in a while when merging on the highway and whats wrong with the occasional 50 to 100 Mph pull, Well Im not real hard on cars but I do drive them and typically my cars last till I get bored with them,
Just sold a 81 Diesel Jetta with 293 on the clock and my 89 Dodge D350 pick up with a cummins with 365k miles on it,
I change oil regularly and burn it in my diesel cars,
My gassers always last too,
So I have no clue why this went, No check engine lights except for the "Stop Valve" didn't close when car was running, Other than that no issues with wagon and only a few weeks before we had it out for a 315 mile highway drive,
? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?
Oh well,
I gave her my 98V70XC to drive for the winter and Ill find something else like a 2000 BMW 325xi wagon,
Ill most likely put the wagon on CL for $600 and let someone have a pretty fresh pair of tires and a good inspection sticker here in PA.
I don't have the time to swap the head as we just bought a house to fix up and my time is better spent in there,

Oh well,
Wife is upset,
But Ill get over it,
Peter

[mtd240]

Bummer. Another burnt valve.

I always run 91/93 octane in our '98 XC. Replaced the O2 sensor at ~130k. Fingers crossed (probably the most beneficial thing I can do to ward off burnt valves).

[E Showell]

I don't mean to perpetuate a mythical connection between failing O2 sensors and burned valves, but I do believe that's what got mine. I have absolutely no way to prove it, however. Regular O2 sensor replacement, not using regular gas and keeping up with oil changes are probably the best insurance you can have -- plus driving above 3,000 RPM every now and again. I also do believe that the valve stem seals just deteriorate with age, although I do not know of anyone who advocates wholesale replacement of them as preventive maintenance -- not saying it would be a bad idea, just that it's a pretty expensive job to pay someone else to do and quite time consuming on a DIY basis, I would imagine (never having attempted it myself).

[rspi]

plus driving above 3,000 RPM every now and again.

I really think this helps.

Purchased my car at 188,000 about 3-1/2 years ago. I run 91+ 98% of the time. I do use HM Mobile 1 10w-40 since my valve stem seals do leak. I usually accelerate aggressively at least once ever other day (3,500+ rmps). No mods, clean PCV, oil changes about every 5,000 to 10,000 miles. I now have 267,000. Car smokes about once per month. Burns about 1 quart of oil every 1,500 miles around town, 1 quart every 2,500 on the road. Replaced o2 sensor at about 260,000. Not sure if it was ever replaced prior to then (with a new one that is).

[E Showell]

I've read it here before. Not sure if it is true, but apparently the valves will rotate above 3,000 RPM, while they do not rotate below that RPM. I think the benefit of +3,000 RPM driving occurs when you operate for a sustained period above that RPM -- say 10 min. or more. I am not sure the occasional peel out from a stoplight at >3,000 RPM provides the same benefit.

[pred]

plus driving above 3,000 RPM every now and again.

I really think this helps.

Purchased my car at 188,000 about 3-1/2 years ago. I run 91+ 98% of the time. I do use HM Mobile 1 10w-40 since my valve stem seals do leak. I usually accelerate aggressively at least once ever other day (3,500+ rmps). No mods, clean PCV, oil changes about every 5,000 to 10,000 miles. I now have 267,000. Car smokes about once per month. Burns about 1 quart of oil every 1,500 miles around town, 1 quart every 2,500 on the road. Replaced o2 sensor at about 260,000. Not sure if it was ever replaced prior to then (with a new one that is).

While this may be true, A good friend of mine has been "Trying" to kill his Volvo, He uses dollar store oil and has deferred regular maintenance, Ever since he lost reverse at 225K miles,,,,
He now has 305K and does drive like an old lady all the time and rarely sees 65 Mph, His valve seals leak like crazy, Idle foe 3 minutes and hit the gas and a BIG long smoky trail is emitted from his tail pipe,
I think this "Burnt #2 Valve" falls under the category of "Shit happens"
Peter