Intake valve cleaner recommendation

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'16.5 Mazda CX-5
My 2016 has 71000 miles on it. When it had @ 20k, it regularly cleared 30 mpg on highway trips, with the best being 32.4. But, I haven't seen 30 mpg in 2 years. Those same trips half-way across the state had dropped to 27 - 27.5.

In preparation for a trip to FLA, I decided to try an intake valve cleaner. I chose an STP product I found at the parts store. Though I'd tried another cleaner at 30k miles, it didn't seem to do much. This time I got good results. The engine seemed to run a little smoother, but more importantly, my fuel mileage improved 2 mpg, or a little more at 65 mph. So, I bought another can and repeated the treatment. After the second treatment I was getting 31.5 mpg on semi-rural highways near home. Cool!

On the trip from TN to the Panhandle I was averaging 33.6 mpg running the speed limit or just under, until I got to the small towns on 2-lane roads near the AL line and finished the trip at 31.2 mpg. I used cruise control as much as possible.

This is the stuff.

71P46dyYAgL._AC_SX679_(2)_1.jpg


It is easy for one person to use. And actually seems to work. Part of the instructions is to drive the car 15 minutes after finishing the treatment. Each time the engine would stumble and miss at some point in the 15 minutes and go into limp mode. Restarting the engine fixed that. Best of all it has restored my fuel mileage to what it was early in its life. I plan to retreat the engine at 30k mile intervals.
 
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GA prior 16 CX5 GT
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20 CX5 GT + Prem
Glad you got good results but the engine going into limp mode is not from the cleaner valves. More likely the gunk either cleaned or coated the O2 sensors which caused the limp mode and probably changed the O2 input to the engine computer which resulted in the mileage improvement.
 
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'16.5 Mazda CX-5
I tried that CRC Product first, at 60k miles and couldn't detect a change.

The limp mode was triggered by a multi-cylinder misfire as reported by the ECU. It was most likely caused by pooled liquid solvent in the intake manifold. It is possible funk broke off of the intake valves and caused the misfires, but passing through the cylinder and exhaust valve would surely have pounded it to dust/mist that could never have affected the O2 sensors. If it had, THAT would have thrown a code.
 
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Pueblo county CO
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CX-5 Sport 16.5 6M
My 2016 has 71000 miles on it. When it had @ 20k, it regularly cleared 30 mpg on highway trips, with the best being 32.4. But, I haven't seen 30 mpg in 2 years. Those same trips half-way across the state had dropped to 27 - 27.5.

In preparation for a trip to FLA, I decided to try an intake valve cleaner. I chose an STP product I found at the parts store. Though I'd tried another cleaner at 30k miles, it didn't seem to do much. This time I got good results. The engine seemed to run a little smoother, but more importantly, my fuel mileage improved 2 mpg, or a little more at 65 mph. So, I bought another can and repeated the treatment. After the second treatment I was getting 31.5 mpg on semi-rural highways near home. Cool!

On the trip from TN to the Panhandle I was averaging 33.6 mpg running the speed limit or just under, until I got to the small towns on 2-lane roads near the AL line and finished the trip at 31.2 mpg. I used cruise control as much as possible.

This is the stuff.

View attachment 298487

It is easy for one person to use. And actually seems to work. Part of the instructions is to drive the car 15 minutes after finishing the treatment. Each time the engine would stumble and miss at some point in the 15 minutes and go into limp mode. Restarting the engine fixed that. Best of all it has restored my fuel mileage to what it was early in its life. I plan to retreat the engine at 30k mile intervals.
Did you try any other treatments, like Techron for the injectors?
 

CarpeDiem

Under Pressure
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Superstitions
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2021 Carbon T
While injectors certainly can get gummed up, at just 71k it is unlikely if decent fuel was used. What the OP is describing is removing the buildup of carbon on the back side of the intake valves due to the lack of a full charge of fuel passing over them. I have trouble believing that the treatment described made such an improvement - comparing mpg is wrought with errors, especially if only one or two tanks are run. But hey, it may have worked great, and the most important part is that the OP is happy with it!
 
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Pueblo county CO
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CX-5 Sport 16.5 6M
Or... Maybe there is something else he tried that hasn't been mentioned.
 
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2013 Mazda CX-5 Sport FWD Auto
I don’t find it too hard to believe. My ‘13 started idling a little rough around 6 yrs, 60k miles. I didn’t lose mpgs but I didn’t like what I was feeling. After removing the intake manifold and cleaning the valves with B12 chemtool, the engine ran smooth as new afterwards. The valves weren’t horrendous. I’d describe them as moderately fouled. I’m doing CRC treatments every 15k miles now to help. Our drives are also much better for the car now after a move to AL. The car was seeing short trips 50% of the time in FL.
 
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Pueblo county CO
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CX-5 Sport 16.5 6M
Some people might prefer to try things like new plugs (@75k miles), O2 sensor, etc.

Is there an easy way to check the intake valves?
 
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2013 Mazda CX-5 Sport FWD Auto
Some people might prefer to try things like new plugs (@75k miles), O2 sensor, etc.

Is there an easy way to check the intake valves?
Agreed. I did my spark plugs first as well. I thought that smoothed things out a little bit too but that might have been a placebo effect lol.
 
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'16.5 Mazda CX-5
Did you try any other treatments, like Techron for the injectors?

Not Techron, it has been ineffective on every port injection engine I've run it in.

I do run a bottle of Redline SI-1 through it every 10 to 15k miles. However, since the GDI never fires the injectors when the intake valves are open, it can have no effect on intake valve fouling. And since the intake valve cleaners never touch the injectors in any real concentration, they won't clean the injectors, either.
 
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'16.5 Mazda CX-5
Back from FL. I ran over the speed limit on the way back, as high as 85, not including 2-lane passes at WOT and still averaged 30 mpg, over 900 miles. There really wasn't a gasoline shortage; we found only one station in Birmingham out of gasoline. But, besides thinking a cleaning was due, I did want all of the mileage I could get if there was a shortage. At home, it shows 53 mpg where it used to show 47.

Unquantifiable, is the feeling that the engine runs smoother and feels like it labors less, like the car moves with less effort. I wish I'd thought to log MAF, TPS and other engine data before, but I never cared about any of that unless I was towing.
 
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Pueblo county CO
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CX-5 Sport 16.5 6M
Do you still have the original plugs?

It sounds like your MPG s have improved a lot.

In preparation for a trip to FLA, I decided to try an intake valve cleaner.
Was there something about your car that suggested intake valve deposits, other than MPG s?
 

Chris_Top_Her

Banned
Moderator
Contributor
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San Antonio, Texas
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'15 CX-5 Miata AWD
I use CRC as it doesn't stall the engine... this makes it much easier to use solo. I also don't use even half the can, because I use it just prior to every oil change.. that should be part of regular maintenance imo, in the same as oil change and fuel system cleaner.. otherwise you end up suckered at the dealer when you valves become caked.