Do I really need to clean my fuel injectors & change my differential fluid?



I have a 2005 Chevy Colorado 4-door truck (great truck by the way). I have 19K miles on it and change the oil every 5K miles. When I took it in for the last service, I was told that as part of the preventive maintenance, I should consider cleaning the fuel injectors because we have “dirty gasoline” and that I should also change the fluid in the differential. Is this sound advice, or a ploy to get a couple hundred dollars out of me?


The authority here is the owner’s manual. All maintenance suggested over and above that listed in the owner’s manual should be considered ADP (Aditional Dealer Profit). While there are a few exceptions in some cases I see no point in what was recommended in your case.


I would answer that in two parts. First, cleaning injectors is done if you think your injectors are in need of cleaning. How are you going to know that unless you have one pulled out and look at it? Today’s injectors are spray nozzles. Fuel is pressurized by the fuel pump in the fuel system and flows through the injector rail. The computer system continually pulses a solenoid in the injectors, very rapidly, allowing small but high pressured amounts of fuel to spray into the cylinders. The pressure remains the same (high) and the amount of fuel is regulated by a pressure regulator and the duration of the injector solenoid pulses. So since fuel is its own solvent, and the solvent is under pressure, there is essentially no injector fouling unless you have an old engine with bad valve seats that is blowing back at the injector. In addition, modern fuels contain detergents that additionally reduce or eliminate the need for injector cleaning, and gasoline is filtered at the pump nearly everywhere in the U.S. If it isn’t in the owners manual, forget it.

Differential fluid is another question altogether. The quick answer is, if you plan to keep the vehicle into the 150,000 to 200,000 mile range, it is a good idea to change the fluid once following break-in (10,000 miles or so). This will remove microscopic metal particles that wear off as the ring and pinion gears polish themselves together. If you don’t keep your vehicles more than say 100,000 miles, you can probably ignore it. There are no filters for the differential grease, so worn metal particles remain in the fluid and become an abrasive. How much that matters depends on how long you want to drive it, and whether or not you tow heavy loads which put extreme pressure on the mating surfaces of the gears. In 100,000 miles of “normal” driving (no heavy towing, no drag racing), you’ll be OK as long as the fluid is not contaminated by driving through water and such, or if you dip the differential into the water while launching your boat on the weekends.


You are quite correct in your assumption that this is indeed a money-seeking ploy. Your service manager will offer these same services to every unwary customer who enters is lair.

In particular, the injector cleaning service is quite unnecessary. Modern gasolines have sufficient detergent packages to do their own injector cleaning. It is possible your car may live its entire lifespan withut even experiencing fouled injectors.

The differential fluid is another matter. Maybe your original fluid is good for a lifetime, maybe not. See the recommendations in your owner’s manual. While you have the manual open, check its recommendations regarding the popular offers of brake fluid flush and transmission flush. Your service manager will suggest these services on your next visit.


Thank you very much for your great advice! This is very helpful and reassuring that I didn’t need to pay for these services at this time.