My wife drives a 6-year old ford focus (petrol) that has started to get really hard on the oil. Filled it up three weeks ago and yesterday the dipstick was basically dry. Its just past 100K miles, and does over 300 miles a week.
In the first place I’m kind of curious as to how this happens - is the oil leaking into the engine somehow? I haven’t noticed any oil under the car, and it is actually driving fine - no blue smoke or anything like that. Filling it up completely every month is getting to be a pain, specially as my wife isn’t really one for checking the oil and she’s doing most of the driving. Whats the straightdope here?
If he’s putting 3-4 quarts per month in it and there’s no puddle under the car, I’m going to guess it’s burning. If it was making it into the coolant system, I would think that the coolant system would be overflowing onto the ground. I suppose it might not do it once it’s parked. I suppose it wouldn’t hurt to take a look at the coolant and see if there’s oil in it, and check the oil for coolant while your at it. I’m still going to guess that it’s burning, maybe not fast enough to have thick blue smoke, burning none the less. Or maybe someone’s stealing it, the cat perhaps.
If it’s going through more than a quart a week, you need to increase your checking & refilling interval. Once the oil level is below the dipstick ou have no clue how low its really getting. And in a high-mileage car a lot of cumulative damage can occur before the low-oil idiot light ever turns on.
You can probably keep the thing running for another 50K miles with an oil habit, provided you don’t, not even once, let it get below the dipstick again.
Change the oil and filter, switch up one weight and buy a case of the cheapest oil at that weigh you can find. You go out every other day and check the oil and find out what the miles / quart usage is and then check at least that often. Do not ever think the wife will do it now if she did not in the past.
Figure out the cost of the oil and the coast of an overhaul and decide how long you want to keep driving that car.
I have found that oil (for engine) and toping up a radiator (water and once in a while some ant-freeze) is a lot cheaper in older cars than the repair.
First, replace the PCV valve. If you’re really lucky, that might solve the problem.
Generally with significant oil loss, there’s either an external leak or internal consumption. Not all external leaks drip a lot onto the ground - most of it might be evaporating (though usually you’ll smell hot oil in that case) or getting blown away while driving. You can tell for certain if there’s drippage by laying a sheet of newspaper or cardboard under the engine area. With the engine warmed up and the sheet in place, run the enine for 15 minutes. For 5 of those minutes, rev the engine to a speed of 2,000 or so rpm. Then shut the engine off and wait at least 30 minutes. Check the sheet for any drips. Whatever the results, have the car thoroughly inspected for any signs of oil leaks. These checks should pretty well establish whether or not there is any significant leakage.
Internal oil consumption is typically either due to worn piston rings or faulty valve stem seals (but be sure to eliminate the PCV valve first). The rule of thumb is that 1,000 or more miles per quart of oil is within the normal range of oil burning, 500 or less miles per quart is bad enough to warrant repair. Fixing worn rings is essentially overhauling the engine - likely cost 2,000+. Replacing valve stem seals usually costs less the 500. Noticeable blue smoke is common with these problems, but is not always present.
Internal oil leakage is pretty much confined to a head gasket breach. There will be noticeable oil in the coolant, visible at the top of the radiator and/or in the reservoir. Usually it won’t lose enough oil this way to account for the amount of loss described.
It can be helpful to get an accurate miles per quart figure. Get the level to “full,” then check it often enough that you can catch it the “low” mark (the difference represents one quart). This is when you want to top up, so until it’s fixed check it at often enough to continue catching it at the one quart low point.
One more thing. Make sure you are checking it correctly.
The most accurate check is done with the car parked on level ground overnight and before the engine is started.
The next most accurate method is on level ground after driving for at least 10 minutes, shutting the car off and waiting at least 2 minutes for the oil to drain back down before checking.
If you don’t follow the same procedure each time you check the oil, you will get inaccurate readings.
I dunno.