620 uses oil

[MattC280Z]

I've noticed my dipstick going from close to the H to down under half closer to the L in a month or so of driving. My truck is a 78 so has the L20B. Have not really noticed any usage before. Truck doesn't smoke at all. Would an oil catch can fix this? I haven't noticed any oil at all underneath when it sets

[Draker]

Well, if you don't see it on the ground.. it's gotta be burning it or in your coolant.

[Draker]

Or.. it's simply just low.

[banzai510(hainz)]

PCV system OK? I seen dumb asses plug the crank case hole

[datzenmike]

Depends on mileage. I've driven 2800 miles in under 4 days and used almost a quart.

 

It can still burn oil and not be noticeable when driving. Stick sheets of cardboard under the truck at night and check in the morning. Leaks are common enough.

 

A catch can is a racing requirement on most racetracks. It's there to collect oil blown out the valve cover vent hose if the engine destroys itself and keeps it off the track. Like a rear spoiler... it's of no use on a street car. If it really served a purpose the car maker would put them in. The PCV system takes care of any blow-by and oil. 

[Stoffregen Motorsports]

It's not uncommon for this to happen "all of a sudden" right after a change to synthetic oil. These old engines weren't designed to be run on synthetic oil as it is very slippery and the ancient ring pack can have a hard time keeping up. That's not to say they can't be run on synthetic, I am just pointing out a common problem.

 

Did you recently start using synthetic oil?

[bilzbobaggins]

Fuel mileage changed any? Wash down of fuel thinning out oil?

[MattC280Z]

Thanks for all the replies guys. I recently put a new PCV valve on, I put synthetic oil in it when I changed it.

 

My fuel economy is usually 26-29 depending on how much i spend driving in town.

 

If this matters i did notice the oil went black very quickly after the change, kind of like a diesel.

[datzenmike]

Check that the choke is fully off when warm. When idling is the fuel level at the mark on the glass on the front of the carb? With mileage like that it would seem like it is not running rich.

 

I don't know what color the smoke is from a synthetic oil... or is there any?

 

Synthetic is fine in newer tight tolerance engines of today but there isn't much advantage to using in out old technology engines, and it's twice the cost or more. That's hard to justify for a small increase in mileage, maybe. A 3% increase in mileage is about 7.8 miles more in 10 gallons or a saving of just over a gallon every 1000 miles. What's a liter? about $8??  If gas is $2 a gallon then if you get 2000 miles per quart you save $4 in gas or about the difference between regular oil and the synthetic. This assumes regular oil is $4. If less than $4 then you loose.

[That4doorKiD]

same happens on my sorry wagon, I just keep adding oil and it turns black :blush:

[Stoffregen Motorsports]

You should switch back to non-synthetic oil.

 

This is also a good opportunity to give the engine a good cleaning. You can add a quart of ATF to the engine, to bring it back up to full, and run that for a couple of days. ATF has detergents that clean the oil scum and it can work into the ring pack and loosen up sticking rings which in turn will revitalize the effectiveness of the rings.

 

I know many people may not like what I have proposed, but it is a tried and tested method to put life back into an aging motor. Be careful though, if you run it too long with ATF, it can actually cause damage.

[datzenmike]

Diesel oil is also extremely detergent.

[MattC280Z]

Sorry to be so late on the update guys the holidays hit me like a hammer lol. I plan on switching back to non synthetic oil once the oil dips to under 1/2 of the safe zone of the dipstick. will update once its done.

[Draker]

Keep us posted. This will be a good experiment. 

[logiccreations]

ima try this on my 620 ill tell you guys how it works mabey have a before and after video.

 

 

ps. i really hop it frees up my rings i cant afford the amount of oil i need to keep it alive!

[scooter]

A liter a month isnt bad, you could throw valve stem seals at it. Go down a long hill and let it engine brake, when you get on it if you get a puff of blue then its sucking oil down the intake stems. Going back to dino oil will help too if its old. The stock ones i had loved rotella 15-40.

 

+1 on the atf, run that stuff in the oil for a day or 2 before you change it and a bunch of shit will come out. I wish i had taken pics of the one motor i did, it was all black and nasty in the valve cover, after an atf treatment and 5000k on diesel oil, it was nice and shiny inside.

 

Oh and if ur gonna atf it dont wail it at 5000rpm on the highway for an hour.. Itll hurt it. Just puttin around at running temp circulating the oil is fine.. Or just letting it idle for a while.

 

Synthetic oil is good for engines that cook the shit out of the oil.. Our engines dont do this.