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

1491 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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In the summer my 2017 Volt will get about 38-40 MPG at 75 MPH. In the winter with the additional drag due to the cold combined with the power requirements to run the blower I can easily see 35 MPG. To improve your MPG, turn the HVAC to Eco once the cabin gets to where you want it, make sure your tires are running between 36 and 40 PSI before you start out, and clear all the ice and snow off the exterior.
I’ll add some air to the tires I ha CB e it set at 34 based on my drivers side door card . Any other advice on long highway driving. I typically do a 10 hour round trip from dallas to Little Rock twice a month so I’ll be doing a decent amount of ICE driving on those trips.
Set the tires to 40 PSI. Also, what year is your Volt - I'm assuming it's a Gen 2 Volt based on the location of this thread in the forum.

I read that using hold mode to keep the battery charge helps for long trips so that the motor isn’t running higher revs than needed. I’m not 100% sure. I have to say this car is by far the most complex car I have owned. Lol. I appreciate you all helping me jump my learning curve.
Again, assuming a Gen 2, don't worry about this. I tend to run my long trips in Mountain Mode simply to provide some battery for off interstate driving, but my experience driving across Kansas is that my 2017 Volt doesn't do a very good job at keeping the battery charged to the Hold or Mountain Mode SOC position at speeds 75 MPH and higher, especially if driving into the wind.
70 seems to be the sweet point for range vs. speed in the Volt.
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