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

1453 Views 17 Replies 7 Participants Last post by dfwvolt, 4 mo ago

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?

https://static.nhtsa.gov/odi/tsbs/2017/MC-10137635-9999.pdf

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!!!

https://static.nhtsa.gov/odi/tsbs/2017/MC-10137635-9999.pdf

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dfwvolt

Discussion Starter · #5 · 4 mo ago

sringlee said:
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.

Are you referring to the Techron that you add to the gas tank? Just want to make sure I’m following.

Based on the design of direct injection I’m sure there has to be some deposit build up since direct injection loses the gasoline “wash down” benefit that traditional port injection has.

i am curious if anyone ever has tried cleaning or had it done at the dealer. When I cleaned my veloster there was sooo much smoke that crap that came off it on that first treatment (noticeably less on the second). It did make that engine drive so much quieter and more efficient afterwards though. I was pretty skeptical of it but my 44 year mechanic step father said it was fine to do. Just don’t stall it or your gonna hate life after😃

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dfwvolt

Discussion Starter · #6 · 4 mo ago

Danno said:
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.

Bingo!!! I forgot to mention I was come from Houston. The windows were fogging up like crazy!! So i was forced into that setting. I also checked my door card when I bought it and it says 34 psi which is where I put it at.

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dfwvolt

Discussion Starter · #7 · 4 mo ago

dfwvolt said:
Are you referring to the Techron that you add to the gas tank? Just want to make sure I’m following.

Based on the design of direct injection I’m sure there has to be some deposit build up since direct injection loses the gasoline “wash down” benefit that traditional port injection has.

i am curious if anyone ever has tried cleaning or had it done at the dealer. When I cleaned my veloster there was sooo much smoke that crap that came off it on that first treatment (noticeably less on the second). It did make that engine drive so much quieter and more efficient afterwards though. I was pretty skeptical of it but my 44 year mechanic step father said it was fine to do. Just don’t stall it or your gonna hate life after😃

obermd said:
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.

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.

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dfwvolt

Discussion Starter · #10 · 4 mo ago

sringlee said:
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.

I agree.GDI is definitely different than traditional and it has is pluses and minuses (this being the main one).

The part I can’t figure out is typically doing this treatment you get the motor hot. Spray in cleaner through intake and maintain engine revs via gas pedal till cleaner is dispersed. Shut off let it heat soak for an hour. Start up and rev the crap out of it and go for a very”spirited” highway drive to heat the cat and then burn off the deposits.
The volt does not exactly let you rev the engine so I’m wondering how it could even work in theory. Mountain mode? Hold? I dunno enough of how it behaves to conjure a guess for that.

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dfwvolt

Discussion Starter · #11 · 4 mo ago

obermd said:
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.

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.

I have a 2017 volt. It sound like I’ll be putting air in the tires and drop my speed to 73 and see what happens. 😃

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dfwvolt

Discussion Starter · #14 · 4 mo ago

Off Oil said:
I have a 2017 Gen2. The tire pressure setting is supposed to be 36, so I think you've got that wrong.

Absolutely correct you are!!! 36 is exactly what is on that placard. I just went out and looked again.

This is adding yet another point to the mounting case for me to finally break down and get glasses

cry:

)

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dfwvolt

Discussion Starter · #18 · 4 mo ago

phattyduck said:
Use 65-70 mph if you want mileage while not being a road block. And yes, 40psi is about the sweet spot for most tires between MPG and harshness.

75mph = low-mid 30's mpg
70mph = mid-high 30's mpg
65mph = 40-ish mpg
60mph = 45-ish mpg

If you wanted good MPG on gas, you shoulda got a standard hybrid.

-Charlie

Well I bought the volt for the city driving in EV mode which is far more economical that a standard hybrid. That said I do make a 10 hour round trip once or twice a month so highway fuel mileage is a factor as well. I did air all four tires up to 40psi like everyone suggested.

I just did a normal trip out to Little Rock from Dallas and used 20 miles in EV before swapping to "hold' mode and I made it there averaging 42 mpg at roughly 70 miles per hour. On the way back my battery was depleted but I managed 40 mpg on the way home at 75 mpg.

Much improved from the first trip up from Houston.

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