The manual says not to use any fuel additives because they could cause premature corrosion in your engine system. According to some of these fuel system cleaner additives, they're supposed to do opposite of that. Does anyone recommend using any fuel additives? If so, what's the best?

 

how many miles do you have? dont throw anything unless its needed and i doubt it is

 

I've had good results with fuel injector cleaners, the kind you put in the gas tank. I suggest you use it only when there is a clear indication of an injector problem. It's not a good idea to use it merely as a preventive measure.

 

I think it isn't a bad idea to run a bottle of Chevron Techron Concentrate ($10) every so often. I usually pour in a bottle once a year and I do notice slightly smoother acceleration each time.


Just don't use this stuff all the time. It might just eat up your fuel injectors. Remember, these cleaners are just high tech solvents.

 

are 4th gen Max injectors pintle or pintleless?

Most aftermarket fuel inj cleaners work safely for both, but there are some that aren't good for pintleless injectors. I've used the Amsoil inj cleaner w/ no problems on all my cars. I use it to mainly clean the intake and exhaust valve carbon buildup.

 

What are the symptoms of valve carbon buildup?

 

4th gen, and later Maximas, have pintleless injectors and are much less likely to get clogged.
Carbon build up (intake valves & combustion chamber) results from gas with insufficent detergents and oil in the intake (crank case vapors - PCV, EGR, leaky valve guide seals). Its effects on performance: blocking/dissrupting intake flow and absorbing the fuel causing a lean condition (intake) pre-ignition & detonation (cumbustion chamber) slowly take place, and may be hard to notice during driving. The symptoms often don't manifest themselves until the engine has high milage. This is why nothing may feel wrong, but it feels better after a can of cleaner.
I'm into putting in a can twice a year.

 

Normal buildup won't cause any symptoms. It will cause a slight increase in the compression test results, but it's difficult to know that the buildup is causing it. It's normal to have some buildup at the valves due to the combustion process. It can build up quicker due to other reasons that brubenstein already listed.

Just toss in fuel injection system cleaner and it should keep buildup to a minimal.

 

I've got close to 90K! I know that's a lot, but it's the only ride I've got, and I've got lots of places to go.