How Adding Too Much Oil Can Be Detrimental To An Engine

A very good article to read.

Interesting a single quart had an effect, especially since it's pretty much accepted that +- a quart is fine. I've never noticed a difference between a slight over or under fill (+-1/2qt) but then again, my engine doesn't even hold a full gallon.
 
Yup! There is a reason that there is the correct amount of oil.
I used to be a member at a Ford truck website that had sub forums on there as well. I usually just visited the 1997-2008 Ford truck forum. There were some members there that had rocks for brains.
A lot of 4.2 V6 engine owners would ask why their dipstick read halfway between full and add a qt. after each OCI. They were adding the correct amount of oil (6 quarts) but still getting a low reading on the dipstick. They would take things into their own hands and add up to 7 quarts. I would tell them that Ford made that "SPECIAL" oil pan just for their engines and threw the mold away. These same members would come back and ask why their oil pressure would drop after doing an OCI. :rolleyes:
My 4.2's dipstick reads between full and add a qt. when I add the required 6 qts. I never add more than 6 qts.
 
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My 1991 F-150 with a 5.0 V-8 is listed as 6 quarts capacity with a full size oil filter. (Fram PH-8A). But if I put in 6 quarts is shows it to be considerably over filled. I replaced the dipstick, and it was the same deal. I drove it on the highway several years ago from Lake Havasu to Tombstone, Az. and when I got back, there was tiny droplets of oil on the back window of the camper shell.

There was no other visible signs of oil leaking anywhere. From that point on I filled it with 5-1/2 quarts, which brought it right up to the "FULL" mark on the dipstick, and never had an issue since. And that was over 25 years, and almost 170,000 miles ago. Go figure.
 
My 1991 F-150 with a 5.0 V-8 is listed as 6 quarts capacity with a full size oil filter. (Fram PH-8A). But if I put in 6 quarts is shows it to be considerably over filled. I replaced the dipstick, and it was the same deal. I drove it on the highway several years ago from Lake Havasu to Tombstone, Az. and when I got back, there was tiny droplets of oil on the back window of the camper shell.

There was no other visible signs of oil leaking anywhere. From that point on I filled it with 5-1/2 quarts, which brought it right up to the "FULL" mark on the dipstick, and never had an issue since. And that was over 25 years, and almost 170,000 miles ago. Go figure.
Same here with my '93 4.9L. During an OCI I put in 5 quarts and call it a day. It will show 1/2 quart low but it doesn't use oil so I'm good to go.
 
Dipsticks and dipstick tubes are not micrometers. I'll go as far as saying they are amongst the most poorly manufactured parts on an engine.

I service a Northstar Cadillac. They require a lot of service. With filter, the OEM specifies 7.5 quarts for refill. It takes 9 quarts to get the oil level to the top of the hatch marks on the stick. Over-filling this motor causes problems. I once carefully measured 7.5 quarts and marked the stick which is just above halfway in the hatch mark. That is full. A lot of makeup oil is added because of the infamous consumption issues these motors have. The owner always filled to the full mark and above. Causes PCV issues, black soot out exhaust and even worse consumption. That and more all went away by following the modified mark on the stick

As for the linked article, Steve Brule' and Westech are featured on Motortrend's Engine Masters. They did an entire episode on oil level. While the article correctly notes that oil pressure stays stable at very high RPM and tiny bits of horsepower is gained, they do NOT recommend running your oil level purposely low on street cars for obvious reasons.

Carefully measure your oil on your next change and mark the stick as needed. That is far better than adding and adding to get the oil level to the top off the full mark.
 
An outstanding source here on this very forum has said that FCA (Stellantis) engines are certified to meet all performance requirements from 1 quart low to 1 quart overfilled. I would suspect most manufacturers have a similar margin of error built-in.
 
If the crankshaft is submerged, it will be slogging through oil causing drag, and throwing oil on the cylinder walls internally which could increase consumption. Some engines have windage trays to keep oil away from the crankshaft. Excess oil being whipped up could also cause oil foaming which could cause wear. Air is not a lubricant if mixed in with oil.
 
If the crankshaft is submerged, it will be slogging through oil causing drag, and throwing oil on the cylinder walls internally which could increase consumption. Some engines have windage trays to keep oil away from the crankshaft. Excess oil being whipped up could also cause oil foaming which could cause wear. Air is not a lubricant if mixed in with oil.
True but you'd be able to tell by pulling the stick and seeing little bubbles or foam it it was ran for a lot. if the oil on the stick is completely translucent no bubbling or foaming occurred.
 
If you double stint a filter remember the engine takes less oil to fill it up. If you put the normal amount in you may over fill it by half a quart. I've seen it happen a few times.
 
Dealer couldn't figure out why I started changing my own oil. Every single time they were over filling the engine by a quart when they did the oil change. Takes six quarts so they would pour in seven to bring it up to full on the dip stick. The service writer was actually arguing with me saying the owners manual was wrong.

The manual states 5.9 quarts wait 15-20 minutes and the oil level should read half way between a quart low and full on the dip stick. After sitting over night the oil level will show full on the dip stick.
 
My truck takes 7.75 quarts...I should be safe just putting in 8 quarts, right?
Wrong. That's typical American thinking. Engineers that built the engine say to use vanilla. Owner says strawberry. Why not just use the factory stated OEM vanilla?

And the person saying oh it's only 3% over full. Over full is just that....... Probably the main and helpful reason the OP posted the initial article to help someone out. I see several here can use it.
 
One I don't get is the 5.3 on 2014+ GM trucks. We have one oil changer who insists on 8 qts, one who insists on 8.2 qts, and most of the mechanics want 9 qts.
Probably sell more oil = $$$$. It's all about price gouging these days.

One ship, I repeat, one ship, turns sideways in the Suez Canal. Entire planet pricing goes through the roof.

Wasn't like ALL the canals were shut down. Just the one little Suez. Which BTW, pushes 12% of our global shipping traffic, ONLY.......... Think about it.
 
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