Fresh oil solves consumption problem

I have a 91 civic d15 that's burned oil since i purchased it. But recently the oil consumption & blue smoke got so bad, at times, that i was convinced that the engine was toast.

http://www.automotiveforums.com/vbulletin/showthread.php?t=680521

But the blowby problem was very erratic-- it was fine, then bad, then fine again.

I'm now noticing that that the amount of blowby is absolutely tolerable when I have fresh oil in the car. After an oil change i revved the engine and got very little blue smoke. It passed inspection without problem-- the emmissions readings don't really look that much different than two years ago.

But after i have 2,000 miles on the oil I get lots of blue smoke.

Has anyone had this experience? I'm thinking that i can get a lot more miles out of this engine merely by changing the oil more frequently. I'm thinking maybe change the oil every 1600 miles and change the filter every other OCI.

(I've already looked at the PCV valve, high mileage oil, engine restorer, etc. I already use thick oil. Fresh oil does not actually 'solve' my problem, it will only reduce it. And I know that eventually I'll need to overhaul or swap.)

I'm attributing this to unburned fuel mixing with the oil through worn rings. The unburned gas contaiminates the oil and it doesn't seal as well (thus causing more blowby).

This article explains it well:

3) The oil becomes fuel diluted with raw gasoline. Gas does not lubricate and an oil filter does not filter-out gas. Gas goes right through undeterred. An oil filter is designed to filter out particulate matter only. Cars that are driven mainly in the city with a lot of low-speed driving, a lot of traffic lights, and do a lot of idling tend to put a lot more unburned gas into the oil. It is common for cars to burn a considerable amount of oil because it has become fuel diluted, reducing its ability to lubricate. Then, because the thinned-out oil cannot seal as well, it will let even more unburned fuel and contaminates past the rings, and more of the oil will burn away. The gas being introduced will sometimes take the 'place' of the oil, and when you look on your dipstick, you see that it is 'full'. This will lead some to believe that their car does not burn oil.

Then, in this example, say you take this car on a 75 mile highway trip and when you get there, you check the oil only to find out that it is 2 or more quarts low! This concerns you, because the car has never burned oil before. So you add a couple of quarts, putting good clean gasoline-free motor oil in its place with nice and new robust additives. You drive home the 75 miles at a little slower speeds because you are concerned about the oil loss. When you get home, you are fully expecting to see a 2 quart loss. But you are surprised to see that it is still on the full mark! So now you are confused. Many will blame the brand of oil, the shop who did the change by installing the 'cheapo' house brand, and some will just scratch their heads in wonderment. Fuel dilution is the culprit. In reality, the fresh oil helped to seal well, lubricate better and prevent excess oil loss.

Thanks for reading.

What weight oil have you been using? Was the 'fresh' stuff a higher weight?

CRX,

I've been using a combination of 10W40 & 20W50. I generally alternate between the two when topping off.

Thinking back, no, the 'fresh' oil was not a higher weight (3 qts 10W40 1 20W50)

I've read on BOBISTHEOILGUY forums that oil consumption often increases during prolonged use.

Another variable wich might account for the inconsistency is the person revving the engine. I don't have a tachometer. So it's not like i can say it starts to smoke at XXX rpm. I've had a couple of different people rev the engine in nuetral while i stand behind it and look at exhaust.

In any event i'm leaning towards advice that you gave me in another thread. Put in 20W50 and drive it. Topping off is certainly cheaper than a swap. I just gotta remember to swich back to a lighter weight in colder months.

I have always found that when I first do an oil change my oil level stays good for 2000 miles, then I have to top it off once or twice before I hit 3000. Oil looses its properties after a bit and tends to become thiner and not stick as well when it gets older.

Ive noticed that as well Hybrid. Oil level stays damn near rock solid for 2k+ miles. Then once I get to 3 its usually almost off the stick.

I have the same problem...get about 2000 out of her then the oil starts to burn...my rule of thumb is I'll top it off with about a quart of oil after it starts to burn, after that I change it...I do a lot of driving and though some say I change the oil too much I don't care...i've had cars given to me that were completely seized from lack of oil...I got my hands on those cars and did oil changes every month or so, depending on the amount of driving I did and got many more miles out of them before the body gave out. If your not cheap just change the oil as often as you can. I'm a firm believer that bad oil is far worse on a car than the abuse you might put them through...I'm sitting at over 300,000kms on my car and its still runs strong

Thanks very much to all of you for responding to this.

Your posts have confirmed my conclusion. My problem can be managed by more frequent oil changes.

With that out of the way i can do the cosmetic work that i've been neglecting for so long (repair scratch, dent & rust. Sand and paint-- try to make it look stock new -- no ricey add ons).