Car burns more oil during highway driving

[Throckmorton]

Okay here's the question, why does highway driving seem to result in more oil consumption. I drive a V6 Accord that normally burns a little more than half a quart in 7,500 miles. I recently completed a 1,500 mile round trip and found that my car burned almost a half a quart of PP. Is there something about sustained highway driving at ~ 80 mph / 2500 in top gear that increases the rate of oil consumption? I always thought that highway driving was easy on motor oil.

 

[JAG]

It's easy on oil because less fuel is burnt per mile and it's at an ideal hot temperature (evaporates fuel and water more readily). Oil consumption can increase because it's an an ideal hot temperature (i.e. thinner and more volatile).

 

[buster]

What JAG said.

I have the 2.4L Accord and drive 100 highway miles a day at 80+ mph. I use 1/2qt per 5k miles on average. It's normal.

 

[JAG]

I've even had the oil level drop significantly during long high speed trips, then after driving to and from work the next day, the level goes back up. Water and fuel buildup in the oil, I think.

 

[ericthepig]

"Water and fuel buildup in the oil"

My Siennas owner manual says exactly that - it states to not be concerned if oil level drops significantly after a long trip - it states this is due to a burn off of fuel and water. (but that seems like a lot of fuel and water.)

 

[Cutehumor]

water and fuel burnoff exactly. makes you think about all those times and the oil was full. half a quart of it was fuel/water

 

[Colt45ws]

Yup. My car burns 1 quart/1000 miles on the highway.

 

[Lonnie]

The threshold for my Civic is 3k rpm. Keep it under and oil consumption is very low, go over and it goes up but that's the cutoff. This car has 392k miles, new valve seals but head never off. The 3k mark is the cutoff.

 

[GMGuy]

If it is fuel/water burnoff, how come I don't experience the same effects when I bump up in viscosity? (5w30 will get sucked back significantly, 10w30 less so, and 10w40 neglegable(sp)).

Alex.

 

[Bullet]

Because at highway speed engine vacumm is tends to increase (at a steady speed) and is pulling oil through the valve seals. some high milage oil or thicker oil may decease consumption.

 

[Steve S]

Quote:

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Okay here's the question, why does highway driving seem to result in more oil consumption. I drive a V6 Accord that normally burns a little more than half a quart in 7,500 miles. I recently completed a 1,500 mile round trip and found that my car burned almost a half a quart of PP. Is there something about sustained highway driving at ~ 80 mph / 2500 in top gear that increases the rate of oil consumption? I always thought that highway driving was easy on motor oil.

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It is.

 

[Gary Allan]

Before I call in the jury on evaporative shrinkage due to fuel or water, I'd run a longer PCV hose just to assure you're not sucking it in the intake during higher sustained loads for prolonged periods of time.

I've often wondered if fuel had some expansive properties when mixed with oil ...sorta like alcohol and water ..but in reverse. It would account for disproportionate volume vs. % of fuel indications. Even if you account for weight/sg differences it would be hard to add up to 1/2 a quart ...or so I reason. I'd like to nail it down with something authoritative. Probably some components of gasoline flash off at 100C+/- ..but I'm sure other components require higher temps.

 

[BuickGN]

I would love to get an answer on this. My TL sees 95% highway miles in the form of a 4 hour trip twice weekly. I've always checked the oil right before I leave for a trip after I've put a few around town miles on it and I've never seen this car use any oil whatsoever. Just checked it after reading this thread and it's 3/8" lower on the dipstick than when I checked it this morning before the trip. I almost topped it off but I think I'll wait until I can check it after a few around town miles.

 

[ARB1977]

My truck has never burned any oil whether its city driving or taking a road trip.

 

[Merkava_4]

Quote:

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Is there something about sustained highway driving at ~ 80 mph / 2500 in top gear that increases the rate of oil consumption?

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Only if you running 0W-20, 5W-20 or 5W-30. Just think of how thin that oil is at 200F whilst you're cruising down the freeway; minuet amounts of it is probably sliding past the piston rings and/or valve guides. But you're getting excellent fuel economy with that Energy Conserving oil.

 

[ThirdeYe]

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My truck has never burned any oil whether its city driving or taking a road trip.

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Same with my car... weird

 

[ARB1977]

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Quote:

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My truck has never burned any oil whether its city driving or taking a road trip.

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Same with my car... weird

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Now my dads 3.4L Tundra burns at least a qrt every road trip (800 miles)...ive always wondered if was because of the short trips he does going and comming home from work. His temps barely start moving.

 

[novaracer69]

i drive 90miles a day all highway in a 04 cavalier it never burns any oil at 10,000 mile oci.

 

[Throckmorton]

Quote:

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"Water and fuel buildup in the oil"

My Siennas owner manual says exactly that - it states to not be concerned if oil level drops significantly after a long trip - it states this is due to a burn off of fuel and water. (but that seems like a lot of fuel and water.)

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Quote:

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I would love to get an answer on this. My TL sees 95% highway miles in the form of a 4 hour trip twice weekly. I've always checked the oil right before I leave for a trip after I've put a few around town miles on it and I've never seen this car use any oil whatsoever. Just checked it after reading this thread and it's 3/8" lower on the dipstick than when I checked it this morning before the trip. I almost topped it off but I think I'll wait until I can check it after a few around town miles.

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Whew. That's a relief. Im glad to see that my oil isn't the only one suffering from "shrinkage". Who would have guessed that the absence of unburned fuel or water vapor can change the volume of oil in the sump by that much.

 

[C4Dave]

I have just the opposite reaction with the Grand Marquis. It usually burns a quart every 1500 miles of short trips around town. But on a recent long trip (1800 miles) with 5w20 in the crankcase, it burned none.