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Carbon build up. Low MPG!! anyone dOne valve leaning?

1456 Views 17 Replies 7 Participants Last post by  dfwvolt
I just bought a used Volt with 51k miles on the clock. (20k of those in gas approximately). I drove it tonight for 230+ miles in gas only. I feel like my 31 mpg for that long a highway drive was pretty lack luster. I was going 75 mpg on cruise. Temps at 40 degrees with max heat and defrost on.

I know theses factors will contribute to lower numbers but I was thinking it would be a bit better than that on the highway. Hoping for around 35-36 to be honest.

in my digging I found out that gen2 is direct injection motor. How I didn’t catch this till now is beyond me. My old Hyundai Veloster was direct injection and I have dealt with carbon build up before. (It’s a real thing)

I found this TSB From GM on dealer cleaning of GDI engines. Very similar to CRC Dorect injection cleaning you can get at auto zone (did this twice on my Veloster with much success)

Has anyone actually had this done or cleaned there valves with CRC or Seafom before?

I am very excited about this new to me volt and entering the EV auto world.

I replaced all the air filters at purchase. Going to change transmission fluid and do coolant change as well. So I know it’s in good shaped. Hoping to see if anyone has any actual experience with cleaning the direct injection. I would like to stay on top of it vs letting it get bad and cause future issues

Seems like everyone keeps saying “just use top tier gas” which I know but I also know that does nothing to reduce carbon on the top sides of thevalves due to the way direct injected motors are designed.

Thanks all for your advice!!!

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If you're running the ICE, it will heat your coolant loop, so there's really no reason to have the MAX button on. The MAX setting can run both your heat and a/c simultaneously and can reduce your mileage. If you're running the ICE, once the coolant temp is above 130, you should have cabin heat, so no need for either ECO or MAX to be on unless your windows are fogging.
Check your tire pressure. Low tire pressures can reduce mpg. Note that the Volt's recommended tire pressures are higher than normal cars. (See inside of door).
I have a 2017. As a reference point, at 75 mph on the highway, I typically get about 38-39 mpg.
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BTW, here's the performance data on the Gen 2 Volt.

Theoretically, we're supposed to get 50 mpg at 75 mph. (see page 5 of the pdf at the link). I've never gotten mileage that high. More like 40 mpg.
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