Underfill or Overfill?

[boone88rr]

This topic came up on another board. I know this has been talked about a few times before but I'd like a few more opinions.

The argument is which is worse? 1/2 quart over or 1/2 quart under?

Now I'm not condoning either. Some people have a tough time reading the dipsticks on the Toyota 1GR-FE. The 4x4 calls for 5.5 quarts. I always drain my oil hot and on a level surface. I put in 5.5 quarts even though I know there may be as much as 0.3 quarts still left in the sump.

I'm under the assumption that being slightly overfilled won't hurt anything.

What do you think? And why?

 

[sxg6]

I think it all depends on the vehicle. I don't know much about those Toyota motors, so I can't say if its ok to overfill them.

In my opinion, i'd rather be .5 quarts under, as long as i was still above the low mark on the dipstick.

 

[CBDFrontier06]

I've overfilled many of my previous cars with no ill effects. Personally, I think there's a margin of error engineered into the dipsticks of modern cars. When I've owned cars that required some odd quantity of oil when changed, I'd just pour in the remaining amount of the last quart and never had a problem. The only time I've ever seen this cause a problem was on an older Olds Cutlass engine where the wrong dipstick was used and the car was consistently, and extrememly overfilled, causing oil to get past the rings and fouling 2 spark plugs. That's never happened on any of my cars with + 1/2 quart overfill. I rather overfill than underfill. Oil is a coolant as well as a lubricator...there's no advantage to underfilling.

 

[OriginHacker21]

Same here - my car requires 5.5 quarts. Manual says: 5.3 quarts, websites quote anywhere from 5 to 6 quarts of oil for my car (2004 Pontiac Sunfire 2.2L Ecotec). If I put 5 quarts in - it is BARELY above the LOW marker on dipstick. 5.5quarts puts it right at full. After a 5,000 mile run - the dipstick reads 1/2quart over full.

But to answer the question: I've talked to several mechanics about this and they've ALL recommended keeping it lower than fuller. But they are quick to say that 1/2 a quart over won't hurt anything.

I believe race cars tend to run a quart high but thats probably because they burn it off after a few miles. Maybe the extra oil helps cool the engine a little bit more?

 

[Triple_Se7en]

quote:

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Originally posted by OriginHacker21:
Same here - my car requires 5.5 quarts. Manual says: 5.3 quarts, websites quote anywhere from 5 to 6 quarts of oil for my car (2004 Pontiac Sunfire 2.2L Ecotec). If I put 5 quarts in - it is BARELY above the LOW marker on dipstick. 5.5quarts puts it right at full. After a 5,000 mile run - the dipstick reads 1/2quart over full.

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If it's overfilled at 5K, you have a leak in there.

 

[Miltellas]

quote:

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Originally posted by Triple_Se7en:

quote:

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Originally posted by OriginHacker21:
Same here - my car requires 5.5 quarts. Manual says: 5.3 quarts, websites quote anywhere from 5 to 6 quarts of oil for my car (2004 Pontiac Sunfire 2.2L Ecotec). If I put 5 quarts in - it is BARELY above the LOW marker on dipstick. 5.5quarts puts it right at full. After a 5,000 mile run - the dipstick reads 1/2quart over full.

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If it's overfilled at 5K, you have a leak in there.

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Or too many city miles and short trips, producing water and fuel dilution into oil. If the engine is more often cold rather than hot then the liquid rinsings could not evaporate off the oil.

 

[rusty 63 model]

My vote is 1/2 qt under. Wouldnt want the chance of the crankshaft turning/foaming the oil any more than necessary. 1/2 qt will only change the oil level in most cars probably by 1/8"-1/4" or less, at rest. I am sure the oil pickup opening would be well below the surface level of the oil in most driving conditions at 1/2 qt low. Of course driving vehicles at sustained G's in turns could uncover the oil pickup opening if the pan is not properly baffled. Have heard of cars running a quart over in such situations. But I wouldnt want to do that in everyday driving.

 

[Clyde65]

quote:

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Originally posted by OriginHacker21:
After a 5,000 mile run - the dipstick reads 1/2quart over full.

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OH21, where is the the extra 1/2 quart comming from?

 

[enjoythemusic]

quote:

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I believe race cars tend to run a quart high but thats probably because they burn it off after a few miles. Maybe the extra oil helps cool the engine a little bit more? [/QB]

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Can only speak for the wet sump track car here... everyone suggests overfill due to possible starvation problem during hard right turns as the oil sloshes around the bottom of the pan. Some also install Accusump to keep the oil going and/or use a modified pan that reduces the oil's ability to slosh around too much.

Oil burning is not a major issue in the car here

 

[acewiza]

It does depend on the engine. My wife's 2002 Sebring 2.7 will leak from what appears to be a front main seal (passenger side/transverse mounted engine) if it is over the ful mark on the stick by much at all. OTOH, I have been overfilling the old V8s by at least a half quart, sometimes a full quart for many many years with no adverse effects - and the side benfit of a little margin for the long trips or the unnoticed small leak.

 

[Pablo]

All things equal, it depends on the engine!

In general there are real benefits to overfilling if there are no leakage issues. I doubt many cars go from normally full to complete oil pan - crank churnage with 1 pt of extra oil!

The benefits of overfilling are: increased dilution of nasties, longer oil life, cooler oil.

I see nothing good about running an engine low on oil.

 

[jsharp]

I'd much rather overfill. Look at how little the oil level rises by adding an extra pint.

 

[Vspec]

Worse yet is a Subaru, I drive an 04 STi and the dipstick makes no sense on a regular basis.

The manual is messed up and calls for 4.2 quarts I believe, while everyone online says that 4.8 quarts is what is required, but when contacting SOA (Subaru of America) they say that 5.0 quarts is the proper amount.

***, I use 5 quarts, I've got an e-mail from SOA saying thats the proper amount, so thats what im using.

 

[heynow]

You could always try filling ot the proper level on the dipstick. Thats why its there

 

[boone88rr]

quote:

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Originally posted by Christopher Hussey:
You could always try filling ot the proper level on the dipstick. Thats why its there

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Thanks.

quote:

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Originally posted by boone88rr:
Now I'm not condoning either. Some people have a tough time reading the dipsticks on the Toyota 1GR-FE.

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[01rangerxl]

A 1/2 quart is not too much to be off by, but I think I would rather underfill since it would still be in the safe range on the dipstick (at least it would be on my vehicle). There could possibly be a marginal advantage to running slightly overfull as far as engine cooling, going too far over full can definately do damage.

Thankfully the dipstick on my truck is always easy to read, the oil level never changes much if any, and the truck always takes exactly five quarts of oil. I have delt with hard to read dipsticks before though, and I feel your pain. I have had similar trouble with certain Nissans before.

 

[BlazerLT]

Overfilling leads to the crank slapping the oil to become partially aeriated and causing air to enter the oil system, where there is air, there isn't lubrication. Also increased crankcase pressure doesn't help either.

Therefore, I always will have my crankcase slightly underfilled than overfilled.

 

[Pablo]

Are you guys really saying 16oz of extra oil will cause crank slapping?

 

[Nebraskan]

Don't worry about a little extra oil. Like it was mentioned earlier, oil is not only lubricant, but holds and disperses heat. They also make aftermakert pans so you can put or hold MORE oil so there is less contaminants in the total volume. 3 quarts over might be a whole lot different story, 3-16 ounces even 32 ounces.. doubt it is anything to loose sleep about. under.. it too, is pretty miniscule to worry about. After all, think about doing a trip and in the advent of one oil check to another the oil was down 1/2 quart. I really don't know anyone that is going to put in a half-quart yet. They will wait for the dipstick to get a bit lower towards 1 quart, and then put in the quart. Common sense rules.

 

[Bullet]

I bought a new truck in 1994 (Dodge Dakoda V6). I don't know where I got the info from, but I've been putting 5 quarts in at every change. The level was always a little over and never paid any attention. Anyway, a few weeks go I wanted to see if I could improve the fuel milage a little with 5w20 and wanted to make sure I didn't over fill. I looked in the OM and it read the capacity with a new filter was 4 quarts. For more than a decade I've been running the capcity over buy one quart. Never had any leaks and ran the same spark plugs for over 10 years (boshe plat). Only time the enging burned oil was when the valve seals no longer sealed, but those were replaced and burns no oil even using the 5w20.