My 1990 F-250 with a 7.3 IDI burns around 2 gallons of oil every 100 miles. No, that's not a misprint. CDR valve not the problem. 6 cylinders 400-460 compression, remaining two are 385 and 310 respectively ~ not adjacent, so not a head gasket issue. I know the 310 is outside the acceptable compression error range, but still can't see that causing that much oil usage. Engine runs smooth, decent power. No metal in crankcase during oil change. Replaced all valve stem seals, not much play in valve stems. With decent compression except the one lowest cylinder, could the oil rings be bad enough to allow that kind of oil burning? Probably have to do a full teardown, but something seems off about that quantity of oil getting sucked into the cylinders. There's some blowby, but it doesn't seem off the charts for an older engine. Any ideas?
7.3 IDI excessive oil usage
- Thread starter Camp
- Start date
@Camp
It might just be rings. Is it a higher mileage unit? Has it been sitting for a long time?
Either way, these engines aren’t too difficult to overhaul, And even if you just found a different engine to drop in for now, you might be a little better off.
Some oil consumption is considered to be normal with these engines, I think due to valve guide wear, but what you’re describing is indeed excessive.
What oil are you using? I used Shell Rotella T6 for a long time, but would have to add a quart about every 1000 km or so. I recently switched to Chevron Delo 400 XSP, and have noticed barely any oil consumption in the 1200 km that I have put on it since that oil change (only a few days ago lol) I think it is down maybe an eighth to a quarter of an inch on the dipstick.
I have heard of a couple of quarts every hundred miles or so, but gallons? That seems excessive. Do you have a turbo? If the turbo seals are out then I could see it drinking a ton of oil.
What makes you say that the CDR is not the problem? Have you replaced it with a new Motorcraft one?
You could always just dump pure Lucas gear oil additive in like ZIPTIESNBIASPLIES (don’t do that lol)
It might just be rings. Is it a higher mileage unit? Has it been sitting for a long time?
Either way, these engines aren’t too difficult to overhaul, And even if you just found a different engine to drop in for now, you might be a little better off.
Some oil consumption is considered to be normal with these engines, I think due to valve guide wear, but what you’re describing is indeed excessive.
What oil are you using? I used Shell Rotella T6 for a long time, but would have to add a quart about every 1000 km or so. I recently switched to Chevron Delo 400 XSP, and have noticed barely any oil consumption in the 1200 km that I have put on it since that oil change (only a few days ago lol) I think it is down maybe an eighth to a quarter of an inch on the dipstick.
I have heard of a couple of quarts every hundred miles or so, but gallons? That seems excessive. Do you have a turbo? If the turbo seals are out then I could see it drinking a ton of oil.
What makes you say that the CDR is not the problem? Have you replaced it with a new Motorcraft one?
You could always just dump pure Lucas gear oil additive in like ZIPTIESNBIASPLIES (don’t do that lol)
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Kevin 007
Full-floater
I see this from time to time when the CDR valve has been confirmed not the problem. Usually some broken or stuck oil control rings. No excessive smoke, just burns the oil as fuel. I have another one here sitting waiting for tear down with the same symptoms. I will bet money to find some broken/stuck oil control rings, and no severe carnage or wear elsewhere.
Thanks for the input.
Kansas IDI....
Yes, higher mileage, though odometer doesn't do hundreds of thousands, but it's been around. Sat for 10 years before I brought it back to life, but was using that amount of oil before.
I've generally run Delo 400 15-40. In the warm weather I even tried straight 50-w ~ made no difference. And, yeah, a quart now and then wouldn't bother me much as these engines'll do that, especially with some age on them.
No turbo.
Back when this oil consumption started I educated the heck out of myself on CDRs. Put a new one on, even blocked it completely at the intake throat to eliminate it, running a hose from the valve cover to release blowby pressure. Normally this kind of oil usage would always be attributed to a bad CDR. I don't recall if I used Motorcraft, but might throw another one on just to be sure.
And Nero....
Yeah, smokes like there no tomorrow, but if I drive it just right, I can minimize the smoking to where it hardly smokes if I'm careful, though taking off from a standing start will leave anyone behind me in a cloud.
I have the glowplugs out from doing the compression test. May as well put some Marvel in there just in case. (I'll let it drain some before starting her up.)
In conclusion, I was just triple checking if there was something I could be missing before tearing the engine down. Just seems like too much oil to be burning given the passable compression readings, but I'm leaning toward major internal ~ rings, cylinder glazing, etc.
Kansas IDI....
Yes, higher mileage, though odometer doesn't do hundreds of thousands, but it's been around. Sat for 10 years before I brought it back to life, but was using that amount of oil before.
I've generally run Delo 400 15-40. In the warm weather I even tried straight 50-w ~ made no difference. And, yeah, a quart now and then wouldn't bother me much as these engines'll do that, especially with some age on them.
No turbo.
Back when this oil consumption started I educated the heck out of myself on CDRs. Put a new one on, even blocked it completely at the intake throat to eliminate it, running a hose from the valve cover to release blowby pressure. Normally this kind of oil usage would always be attributed to a bad CDR. I don't recall if I used Motorcraft, but might throw another one on just to be sure.
And Nero....
Yeah, smokes like there no tomorrow, but if I drive it just right, I can minimize the smoking to where it hardly smokes if I'm careful, though taking off from a standing start will leave anyone behind me in a cloud.
I have the glowplugs out from doing the compression test. May as well put some Marvel in there just in case. (I'll let it drain some before starting her up.)
In conclusion, I was just triple checking if there was something I could be missing before tearing the engine down. Just seems like too much oil to be burning given the passable compression readings, but I'm leaning toward major internal ~ rings, cylinder glazing, etc.
Kevin 007....
Makes sense (except mine does smoke, but with that amount of oil going through, I'd expect that). And yeah, what's baffling is the engine runs smooth, never misses, sounds great, zero metal particles on the drain plug magnet, so it makes sense there may not be other severe internal damage. I've never been that focused on oil rings as compression usually goes first, but in this case, it's the reverse. And maybe the second ring which I guess is an oil stripper ring, like Nero suggested.
Makes sense (except mine does smoke, but with that amount of oil going through, I'd expect that). And yeah, what's baffling is the engine runs smooth, never misses, sounds great, zero metal particles on the drain plug magnet, so it makes sense there may not be other severe internal damage. I've never been that focused on oil rings as compression usually goes first, but in this case, it's the reverse. And maybe the second ring which I guess is an oil stripper ring, like Nero suggested.
Kevin 007
Full-floater
Im suspect that ether use at previous times in these engines lives could have broken rings to cause these problems, but maybe not the compression rings, giving an engine that still runs good, just burns oil like there's no tomorrow
Its crazy how well these engines still run with no piston rings and no hone marks. The first engine I swung into my dads truck we later found out it ate a bunch of dust, was going through a quart of oil every 100 miles, took it apart to find zero hone marks and cylinders all ovalled out, but it ran without skipping a beat.
IDIBRONCO
IDIBRONCO
It would probably be better to add some to your oil.
Copy that. Not expecting it to solve things. Be interested to know if anyone ever fixed this kind of oil usage with an additive. Pretty sure it'll take a teardown.
IDIBRONCO
IDIBRONCO
No promises, but if your rings are stuck, it could work.
Easy enough to do. I'll give it a shot.
Old Goat
Full Access Member
I use a qt every 600 miles. It`s been using that amount
for a long time. Up to 354K now.
You have the engine experts on it now, never heard of
anyone using the amount you are using.
Goat
for a long time. Up to 354K now.
You have the engine experts on it now, never heard of
anyone using the amount you are using.
Goat
