I took my HCH to the dealer for 40000 mi service and got it back with the oil about 1/2 inch higher than the top mark on the dipstick. I've seen mention in these threads of oil level being an issue for FE, and I see in the owners manual that overfilling risks damaging the engine. I suppose they tech was too lazy to add the proper 3.4 qts and just dumped in 4 instead, and I think it has probably happened every time (at least twice before). So what's the story? Does it really affect FE? What kind of damage is possible?

Dave

 

overfilled sumps mean the level could be high enough for the moving parts of the engine to splash the oil around, causing air to become entrained in the oil- like shaking a paint can instead of stirring.


Besides the obvious drag on the moving parts having to slog through liquid, this also reduces the amount of lubricant actually getting to where it needs to be (air displacing some oil as it gets pumped around), and causes it to get hotter than it would normally be (air having a very low specific heat)

Catastrophic? Probably not. But certainly suboptimal.

 

That's why I always hand the techs the exact amount of oil. Mobil 1 0W-20 of course. That way they can't overfill.

 

Unless they knock it over, and then "fill it up" with who knows what!

Man I just can't let people change my oil...so many stories about lazy techs.

But there's also a lot of conscientious folks out there too. I just figure they let the "new guy/gal" do the oil changes, and that's reason enough for me to crawl under our car and do it myself.

 

[QUOTE=gonavy]overfilled sumps mean the level could be high enough for the moving parts of the engine to splash the oil around, causing air to become entrained in the oil- like shaking a paint can instead of stirring.

Thanks for the input Gonavy, but I've always imagined some moving parts (bottom end of con-rods) dipping into the oil reservoir, even with low oil level. Is that not correct? And I fail to see how it would make a measurable effect on fuel economy. Certainly it's a matter of degree, and if the level is high enough the sump could get really chaotic, but at 1/2 qt high?

The Nat'l Championship Air Races are in Reno this week. Maybe I should corner an aerobatics pilot to ask whether they have concerns about oil's behavior in their sumps.

 

Maybe he did fill it with the correct volume but some/most engines will still hold an amount of the old oil when drained. You can remove the over-fill if you can get to the drain plug on the sump but be careful - it can be difficult to get the plug back in when the is oil coming out at full flow - the last thing you want is a driveway full of oil and no means of transport to get some new.

My car has been overfilled on the last two services and I have trickle drained it down to level (half way between max/min ) by undoing the drain plug a few threads. Half an inch over on the dipstick equated to more than a litre over-fill. Too much oil can create excessive pressure leading to leaking gasgets.

I would service most of car myself if there was no risk of voiding the warantee but instead I spend all of what I save on fuel bills on over-priced servicing by what appear to be monkeys. Hey-ho, next time I will get an older car beyond warantee and save myself even more money.

PS. A lower viscosity oil than what is originally specified for your vehicle WILL improve fuel economy.

 

If they are using the quart bottles of the special oil I dont see how it could get overfilled. I know most dealers use bulk oil from a tank for regualr oil changes, but the HCH takes special oil so I would think they use the bottles.

 

[QUOTE=solecondad]
it is a matter of degree.

Aircraft engine lubrication is a different beast entirely. Many use pressurized sumps to ensure flow to the suction side of the pump. Those that don't, or don't use some other system to ensure flow, CANNOT fly 'upside down' for any extended period- low oil pressure will cut the engine out.

Aerobatics are probaby fine- short periods in odd positions, and very specialized aircraft.

 

I was doing an oil change this weekend and accidently overfilled the oil. I don't know what I was thinking when I kept adding oil until it came up to the line on the dipstick. Once I backed off the ramps and checked the oil level it was of course over the top line on the dipstick. I found a nifty little pump at Pep Boys to pump the excess out the dipstick tube. Worked great. For anyone interested, it's called the Mityvac. (P/N 07240) It sells for $12.99.

Rich

 

good move. by that I mean that is a cool tool and you are better off doing that then leaving too much in.