trhs75

My daughter's '99 has 145,000 miles and has not used oil in around-town driving since we got it about five years ago with 115,000 miles. However, now that she is driving to college, it uses an unusual amount of oil in highway driving. This weekend, it was 1 quart of Mobil1 5W-30 every 434 miles at about 65-70 mph. While she's driving around in town at school, consumption drops to almost nothing again.

The car doesn't leak oil at all. I see no signs of oil burning -- no smoke at startup or while running, no odor when driving behind the car. I'll probably have to take it to the dealer when she's back next summer and have her continue to keep an eye on the oil level in the meantime.

At the last plug change (shortly after purchase), the old plugs look clean and dry.

Anyone have any ideas? Thanks!!

code58

Have you checked the PCV valve? If it is stuck it can cause excessive oil consumption. There is a new design rear valve cover (that's the one the PCV is in) that I believe is supposed to take care of excessive oil consumption. Do a search for it, you should be able to find details on it. Make SURE she checks the oil every week or so til you get this resolced. You definitely don't want to have to buy a new engine for it.

You might alaso want to consider changing to another oil. There HAVE BEEN documented cases of heavy oil consumption with Mobil 1 from the very begining, though it is pretty rare.

hypervish

Run Pennzoil Platinum 5W-30. And, like code58 said check the PCV valve. You might as well replace it, as it is cheap.

I had the same issue with Mobil 1 5W-30, I added almost 2 quarts during my monthly drive to Michigan/Chicago.

That was about 2 years ago, since then I've been strictly using only Pennzoil Platinum and I haven't had a single consumption issue. And, I drive 2000 miles highway every month. At one point I drove 3800 miles in a week span, and still the level didn't drop one bit. But, as soon as I got home I changed the oil, I rarely ever go past 4k on an oil change.

I recently purchased some Pennzoil Ultra on sale, so I'm going to give that a go and see how it fares. I recall using it once a long time ago, and I think it did well and didn't have any oil consumption issues.

I wouldn't be surprised though if sometime soon my RX started consuming oil, it does have 187k miles on it now.

lexus114

Heck your good at least until 220K before anything like that will happen.

hypervish

Haha, very true.

trhs75

Thanks, guys! I really appreciate the input. I've been wondering if that synthetic is a little more prone to disappearing. I use it in everything else. I'll stock up on the Pennzoil Platinum for the RX's next change!

code58

You underestimate modern cars and oils. True story, my SIL had a Dodge van (she purchased new) from the 80's. By the time she traded it on a new one it had 360K mi. on it and had started to use a little oil then. NEVER had the heads or pan off !!! She put a lot of miles on her vehicles but my brother would have a hard time getting it away from her long enough to do maintenance on it. If a Chrysler product will do that, you should be good for about 6-700,000 mi. before problems arise.
My experience with full synthetic is it GENERALLY uses almost no oil. It can be a bit strange, so if it uses it in one brand, try changing brands, it may use none.

trhs75

Yes, that has been my experience up to now, also. I don't have the advantage of knowing the entire history of this car, unlike the ones I "started" from new, so that may have something to do with it.