What's the rate of evaporation/loss of a full synthetic engine oil?



I’ve got a 2003 VW Passat (2.8L V6 model) and I use Mobil 1 Full Synthetic oil (0W-40 grade). Assuming there is no leakage from the engine (I do the oil change myself and did not see anything leaking … all clean) how much of the oil can I expect to lose over time? Over 3 months? 6 months? (Assuming I do not drive over 5,000 miles).

Thank you.



All engines pass at least a wee bit of oil to the combustion chamber. How much depends on the individual car, how many miles it has on it, as well as its driving environment. On a 2003 it’s impossible to guess.

Assuming you just got the vehicle, you need to check your oil every few days until you get a “handle” on what your normal usage is. Anything from a quart every 1,000 miles to no significant usage would be normal. City driving tends to be more becaues it spends

By the way, it does not evaporate. It gets burned. There’s always a miniscule amount that remains on the cylinder walls after the oil rings pass by and provides some lubrication for the compression rings, and that gets burned in the cylinder along with the fuel.


Wow! 0W-40? Haven’t seen that on the shelves yet.

Oil consumption is dependent on several factors. Viscosity, engine break-in, average RPM, tempertures, and to some degree, metallurgy. Ignoring the latter 2 for now, the thinner the oil at operating temperature (the 2nd number in the viscosity rating) the more likely the oil is to pass the rings. Higher average RPM means more piston trips up/down and hence more combustion cycles and more oil consumption. Higher revving small engines will use more oil than larger engines, all else being equal. Then there is the piston travel, bore diameter and the mathematical considerations of exposed/swept cylinder wall area.

Engine break-in is, in my experience, the most critical. Most manuals tell you to drive with varying speeds for the first 500 miles or so. This varies piston ring loads and helps rings to seat properly under constantly changine load/no-load conditions. The very worst thing you can do is to take a brand new vehicle out on the highway, set the cruise at one steady speed and drive for hundreds of miles at the same engine RPM. That’s why I would never buy a “new” vehicle that had been ferried across the state from another dealer. I get blown off the road frequently when a new vehicle flies by with a temporary dealer tag on the back.

I properly broken-in engine shouldn’t lose more than a quart of oil between changes. I’ve driven cars for many years now, most of them purchased new and all of them traded at over 150,000 miles and never needed to add a quart of oil at 3-4,000 mile change intervals. My current 6.0L LS2 uses about 3/4 quart in 4,000 miles with Mobil 1 5W-30.


VWs of your vintage are renowned for burning oil. VW claims a quart per 1,000 miles is “normal.” Good for them.

My Honda, with >70k miles, loses virtually NO oil between 5k miles changes.

Drivers wanted!

Whatever you do, don’t neglect to check the dipstick every two weeks or so!


Thank you for the information. I didn’t know about the quart per 1,000 miles.

FYI - my Passat has about 44,500 miles on it now. I changed the oil almost exactly 5 months ago at 40,500 miles. So, it’s been driven about 4,000 miles now (about 75% city driving). Yes, it’s not being driven much.

The reason I asked the question was because just last week, I noticed that the oil level had dipped below the minimum level and was barely covering the plastic end of the dip stick. I was rather shocked, because 5 months ago, I had put in 5.5 quarts of that synthetic oil. I checked where the car is normally parked and there is no oil drop or residue on the concrete floor. I was almost wondering whether the garage where I took the car to for spark plug replacement at 41,000 miles drained the engine oil, because I’ve been doing the engine oil change on my two VWs for last 20,000 miles or so and I’ve never seen the car lose that much oil before. I was actually quite surprised that the “check engine oil” light did not come on.

Anyhow, I’ve not experienced the 1 quart per 1,000 miles yet … until this time. And I’ve been using the same grade 0W-40 oil ever since I started doing the oil change myself.

Any thoughts?

Thank you.


5 months between checks is too long. McP’s recommendation of every two weeks is good, I check mine about every month.

The fact that your oil light never came on is a great sign. It means you’ve done no damage. The way the system works is that there is that all of the oil in the engine circulates through the parts lubricating them and then drains down into a pool of oil in your oil pan. The oil pump has a tube that sticks down into the pool and pumps the oil under pressure through the engine. The oil light responds to a pressure sensor that’s in the pressurized side of the circulation, just past the oil pump. It does not respond to the level of the pool in the oil pan. As long as there’s pressure it means oil is being pumped everywhere it needs to be. In short, your engine is fine.

However, you still need to get in the habit of cecking your oil level. Personally, after I’ve chenged my oil I check it multiple times for a few days until I’m certain that I haven’t left a leak. Anyone, even I, is susceptable to overlooking a faulty O-ring on the filter.

Hope this helps.


I also have a 03 Passat V6, 53Kmiles. I’ve never had to add oil between oil changes (5Kmiles). Use regular oil, whatever the dealer has.


Check your oil/top if needed every 2nd or 3rd fuel fill up. Your vehicle will last a substantially longer time.


Ideally a car will loose/burn less than a quart every 2-3,000 miles. Most do that good, but some don’t. It is dumb luck. If it starts consuming more without reason (like long hot trips etc.) then you may have a problem. It may well be burning it and if it does not burn too much you will not see any smoke and it will not cause problems. When it starts burning too much you can damage the converters and/or start seeing smoke.

BTW evaporation rates would be measured in thousands of years.


My car has 180,000 extremely abusive miles on it and it burns no oil at all, none of my 12 + cars over the last 20 years used any oil at all except for my Toyota P/U with the 22 RE with 208,000 miles of plowing snow and towing cars with it. It was burning a quart every 500 miles until I switched to 20w50. Now it burns a quart every 1500 miles.
I think your problem is your using the wrong oil. Synthetic oil is way over rated unless your engine has a turbo, if it is a turbo, just use a heaver weight oil. Try using what the Factory recommends (non synthetic) or a little heavier. Lastly, always change the oil every 3000 miles or less. I?m an ASE Certified Master Auto Tech with 28 years in the business and I have seen this problem before, the cause in most cases is do to the use of synthetic oil. Regular cheep oil works great.


For my 2004 Passat VW requires a specific grade of synthetic or the warranty won’t be honored. I would definitely not switch to anything else. The owner’s manual should say what’s required for a 6 cylinder.


The rate of evaporation of any motor oil is very low; too small to measure. If your oil level goes down, it is either LEAKING somewhere, or it is slowly BURNING in the cylinders. You may not see the small leaks, since they often occur when the car is being driven and is thoroughly warmed up.

A car can use oil without showing any blue smoke; very low oil consumption at highway speed will not show any blue smoke.

In a perfectly broken-in engine with no leaks, your oil level should stay right up for at least 3000 miles. It did for 5000 miles on my Toyota.

You did not state how many miles are on your Passat, and if you have owned it since new. You also did not state your driving pattern, e.g. short trips, long trips, etc.

In any case, if it does use 1 quart in 2000 miles don’t worry, jut top it up. This is nothing unusual. But it is NOT EVAPORATING!


I have an Audi A4 that has 102k miles already. I lose oil: a bit less than half a quart every 1,000 miles. The car is being driven mostly around town, 6-7k every year. I use the Mobil 1, 10W40, as recommended by the manufacturer. My main concern is that the oil loss, burnt most likely, is due to engine wear. I could find a college kid that would buy my car despite the oil burning, but I rather keep it. The question is would it last 30,000 more miles without engine rebuilding? Should I switch cars with my husband, he drives on faster roads and highway, to extend the engine’ life? I appreciate any comment.


I have an 03 passat V6 also, never added a drop of oil (5k interval)