Worse MPG after oil change... why?

probably run the battery down while they're at it

 

That would never account for 1,000 miles of difference. The battery will charge on one drive.

 

depends on the drive

 

10% higher fuel burn for 1000 miles. Assuming the car was getting 50 mpg, now it's getting 45 or so. So, instead of 20 gals burned for the 1000 miles, it's 22.2 gals. I doubt it takes 2.2 gals of fuel to charge the battery from whatever amount of slight discharge it might have suffered.

Perhaps somebody is swiping a little fuel while the car is in for the oil change.

 

@Preeeus you've been having high oil consumption (just looking at your previous postings). Is it a dealership doing the oil changes, and maybe they're cognizant of this, sending you on your way significantly overfilled? Do you check the level when it's settled down, a day or two after the oil change?

 

Excess oil reduces fuel economy? How can that happen?

 

It would have to be a huge over-fill so the crankshaft weights hit the oil in the pan. That would create drag.

 

Maybe they adjusted the tire pressure down.

 

Once oil change is complete, but before closing the bottom panel opening, instructions say to put the vehicle in “maintenance mode” which I assume runs the engine so you can check for leaks. I’m guessing this hurts average MPG as well, if techs actually do the step. I don’t so I’m assuming they might not as well.

 

Ah so you're doing another oil consumption test as well? Here's hoping you pass, I mean fail, I mean, oh you know what I mean, lol. Have any steep hill-climb routes in the vicinity?

 

Hi! Max here from MaxJen International.
I just want to double check with you about the oil level. They drove it up to you at the front of the shop, pulled the stick to show you the oil level within how much time?
If its showing a full mark level within 5 min you stop the car, I'm betting they over filled it by at least 500ml or more. Everyone knows oil level checks are done on even surface and at least 15 min after you stop the engine.

Another issue is, once cars go in for service you can kiss your millage for this current tank goodbye. Dont bother reading it off that tank no more because they would have depleted your battery, burned lots of fuel to do the maintenance mode to heat and drain the oil, and run it again to check oil level, plus swing by to the fish and chips with the customers car.

So do a new tank and see, plus dont let them overfill your oil again. Oil overfill causes oil leaks by blowing gaskets and burnt rings will burn oil.

 

He's got a lot riding on this oil change. They've done an oil change, checked that the level is on the full mark (hopefully accurately), and applied tamper-proof seals to all the places oil could be nefariously extracted from the engine.

When he goes in Monday, just shy of 1300 miles later, they'll break the dipstick seal and recheck. If it take more than a quart to return the level to the top mark, he "wins". The prize being a complete engine overhaul, involving new pistons and rings, head gasket and so on.

More info in the attached; 168 is the test, and 169 the overhaul instruction.

 

Wow that is crazy!
Top end rebuild.
Are you getting oil gunk out the exhaust? If you do I think you going to win!

 

I think I'd be finding a way to have that car back at the dealer with 1295 miles added on.
From my house to Atlanta is almost exactly 200 miles. Sounds like I'd do 3 high speed round trips and park it. Then roll around locally and take it to the dealer with 1295 on the clock.

 

Could I add that on traditional ICE cars, an oil overfill sufficient to have contact of crankshaft pieces with the oil surface would typically cause oil foaming and crankcase over pressure that would in turn blow oil through seals such as crankshaft end seals , possibly damaging them. I assume this would also happen in Prii. So, something to be avoided.