My Bronco has 129K miles. I have all of the service records since new. It has always been properly maintained, and dealer serviced up to 70K when the original owner sold it. The original owner changed the oil and filter every 5,000 miles, which is less than the factory recommends for normal service. The original owner was a lady who did not use it hard, and it did not need to be on the severe duty schedule. Since she sold it, the oil and filter have been changed every 3K to 4K. I change it around every 4K because a lot of my mileage is highway, and I don't do much stop-and-go driving or encounter traffic jams.

My question is, should I run a can of Gunk engine flush before my next oil change? I have been "cleaning" the engine over the past 3,000 miles by running a can of Seafoam in the crankcase, and three cans of Seafoam in a full tank of gas (32 gallons). The truck runs fine, I did not put the Seafoam in to try a last-ditch effort to fix something. I just put it in to do a good cleaning the engine and fuel system.

I would imagine that the engine is pretty clean inside, due to the fact that it has been properly maintained all of its life. The engine oil never goes black. I am just worried that a can of engine flush might dislodge something that could mess up the engine. It runs so well now that it would be a crying shame to ruin it with a flush. So given the maintenance history of the truck, do you think that I should run the flush?

 

Considering the maintenence history I would say no, "If it ain't broke" is probably a good thing to adhere too.

 

I just checked the owner's manual to be sure, and the oil change interval is 7,500 miles for normal driving. Looking at the records, I see that the truck has had the oil changed at 5,000 or less since it was new. I doubt that the woman who was the original owner ever even took it off road. All of the front end suspension components are original, and every time that the front end has been checked since I purchased it no problems have been found, the last time was in summer of 2004. The truck feels and drives very tight and has no clunking sounds from the suspension and tracks straight down the road. And it was kept in a garage as well. It seems to have lived an easy, adult owned life. Of course, the front end and garage storage have nothing to do with the oil; I was just demonstrating how the vehicle has been driven and maintained since new.

 

Don't use any of the engine flushes. It is usually just diesel fuel (or kerosene) that is made to BURN, NOT LUBRICATE! You could use a diesel rated oil if you wanted. It will clean the engine but it will do over a longer period of time (which is what you want). Good luck!

-Matt