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

1455 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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The Volt is a direct-injection engine. Most GM cars from 2000 on use injection in the intake manifold which can create deposits on the intake valves. The TSB refers to those engines, not DI. That noted, it is probable that direct injectors can become coated with carbon or deposits. The occasional can of Techron will ensure the injection spray is correct.
I stand corrected... GDI engines can suffer carbon buildup on intake valves thanks to the EGR, which allows oil mist to recirculate through the intake system. It appears there might be ways to remove it using spray cleaners and cleaning kits but you will set a trouble code that needs to be cleared. Using Top Tier gasoline and the correct synthetic motor oil will help. This topic needs more study for Volt applications.
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