Random improvement of gas mileage?

[StealthyKDM]

Today when I started my car after I got off work I noticed it said 12.0 average mpg. I did let the car idle when I was on my lunch break for it to be saying 12.0. But on my way home, I'm driving normally, light acceleration and I look down and it now say 18.0 then it jumps to 22.0. I don't drive on the freeway just the streets to get home and work is about 3 miles.

This has never happened to me bedore, the highest average on the streets was 16.5. This week I am going to have the dealer clean the carbon buildup because I have been wondering why I have been getting bad fuel economy.
My genesis is a 2012 with 88100 miles on it.

 

[Mr. Incredible]

usually the jump around means the MPG average has been reset, so it takes awhile to settle back down to a real average, usually a couple hundred miles.

I don't know about your 1G Genesis, but on my G80 there is an option to auto reset after filling the tank, I turned it off else all I will ever see is the average for that tank and not the overall average over a long period of time.

 

[QuantumRift]

It's not a problem. Once in a while my mpg cpu will go wonky and do that. Don't be alarmed...all I do when that occurs is perform a manual reset on the MPG. The the cpu mpg is off anyways (I always calculate by filling and recording data and calculating mpg manually). You're NOT getting 'bad fuel economy'. Just reset the mpg display and watch for trends. That mpg display is OK, but it's always better to manually calculate and just use the cpu mpg thing to look for trends. RESET IT.

As for the carbon buildup on the valves, look for the sep threads we've been discussing this. I just did mine (76K miles and never had one) with a can o of CRC intake valve cleaner...and will do another one soon. I expect I will actually remove the intake plenum and manifold and manually spray the the valves as well..save yourself $100 or more. All I an say is that the CRC stuff does seem to be formulated to dissolve carbon.

And once you do that, INSTALL an oil catch can to prevent or reduce further build up.

GDI Gas Direct Injection


d

 

[RemyBluePearl]

It's not a problem. Once in a while my mpg cpu will go wonky and do that. Don't be alarmed...all I do when that occurs is perform a manual reset on the MPG. The the cpu mpg is off anyways (I always calculate by filling and recording data and calculating mpg manually). You're NOT getting 'bad fuel economy'. Just reset the mpg display and watch for trends. That mpg display is OK, but it's always better to manually calculate and just use the cpu mpg thing to look for trends. RESET IT.

As for the carbon buildup on the valves, look for the sep threads we've been discussing this. I just did mine (76K miles and never had one) with a can o of CRC intake valve cleaner...and will do another one soon. I expect I will actually remove the intake plenum and manifold and manually spray the the valves as well..save yourself $100 or more. All I an say is that the CRC stuff does seem to be formulated to dissolve carbon.

And once you do that, INSTALL an oil catch can to prevent or reduce further build up.

GDI Gas Direct Injection


d

When using CRC did you spray it into the throttle body or the air intake? Also is using the Vacuum port another way of getting CRC into the engine?

 

[dougmcp]

I'd scratch the dealer carbon clean and give it the old Italian Tuneup. A spirited run to San Diego at speed and lots of full throttle should do the job nicely.

 

[Starflyer]

Today when I started my car after I got off work I noticed it said 12.0 average mpg. I did let the car idle when I was on my lunch break for it to be saying 12.0. But on my way home, I'm driving normally, light acceleration and I look down and it now say 18.0 then it jumps to 22.0. I don't drive on the freeway just the streets to get home and work is about 3 miles.

Idling kills gas mile. Earlier in the week, I filled my tank and drove a few miles around town. Then I stop to to learn how to program the GPS on my new '18 G80. I started out with the engine off and soon got the battery warning that I think said if I continued, I would drain the battery. So I started the vehicle up and left it idling while I finally figured out how to program the GPS. I think with I started with the battery off, the trip computer said I was getting around 20 MPG when I turned the engine on to prevent draining the battery.

When I finished with the GPS, I went to a neighborhood gas station to fill up. Bare in mind, the tank only took 4.142 Gal to fill. At that time, the computer said my gas mileage was 12.7 MPG. Figuring it the old fashion way, I came up with 14.5 MPG. With the tank only taking 4.142, I knew both mileage figures were not very accurate other than idling EATS gas.

 

[QuantumRift]

While it sounds good, I don't think that you an blow the carbon out of a Genny that way.

I do remember back 'in the day' that my uncle would say, "Hey Doug, I'm gonna go blow out the carbon, wanna ride along"...and of course, I'd say YES and my mom would be petrified (I had no idea what 'blow the carbon out meant) but I soon realized it was just an excuse to go speed like hell out on the back roads. Nowadays, you say "Honey, I"m gonna go blow the carbon out of the engine" and all you get is 'Yea, right'. LOL.

I'd scratch the dealer carbon clean and give it the old Italian Tuneup. A spirited run to San Diego at speed and lots of full throttle should do the job nicely.

 

[Gunkk]

The good ol' italian tune up

Nowadays with DI cars going stupid rich at WOT (especially boosted DI cars), you're more likely to do the opposite.

 

[dougmcp]

My solution was somewhat tongue-in-cheek but to be honest the only thing short of doing a walnut shell blast on a CDI engine is an Italian tune up with maybe something in the fuel to burn or wash off deposits from the back of the intake valves. Possibly a catch can may stall off the inevitable.

 

[QuantumRift]

Yea a catch can will remove a LOT of those oil vapors that condense into deposits. CRC, from what I saw, does a damn good job at dissolving them.

My solution was somewhat tongue-in-cheek but to be honest the only thing short of doing a walnut shell blast on a CDI engine is an Italian tune up with maybe something in the fuel to burn or wash off deposits from the back of the intake valves. Possibly a catch can may stall off the inevitable.

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