Well Champions are great in say a Chrysler in line 6 engine as they are the OEM for those engines. And many people still push Champion for these engines to fix the two piece design but too many people have issues. I wish you luck with the change and that everything works out.

 

I'm ordering Motorcraft today, I'll let you know how the swap goes. RockAuto replied they are aware that Ford products have issues with non-OE parts such as spark plugs but they continue to recommend these parts for replacement. Obviously they care more about the buck than customer satisfaction.

 

Most parts stores, RockAuto included do just that. I always research the correct plug for any application before buying. If I went by what they want to sell me, I'd be running $12 a piece plugs in my 86 F350.

 

x2 on the OEM parts. Especially plugs, I tried autolite to save a couple bucks. within 15k miles my truck started missing. got FMC plugs and swapped them, found 2 autolite plugs burnt. BTW both changes, no broken plugs. 1st change @80k 2nd change 105-110k

 

Try gapping your new plugs to the same as the ones you replaced, not as specked.

 

I would think there is a problem with doing that. The gap is no longer the same as when it was originally set when the plugs were installed. I would get the correct heat range plugs and set the gap according to what is specified by Ford.

 

I don't think you can gap these Motorcraft plugs?

 

No gapping on MC plugs. Also note that the TSB on the plug change says specifically to apply the anti-seize to the shield section below the threads. It does not reference applying to the threads, though I do not know why it would cause a problem.

 

16mpg-->13mpg = 20% drop in mpg. Something else might be going on too. If the plugs are culprit, is the truck running rich? If you have to do emissions tests, how were the HC levels on the last test?

When I changed my stock BFG tires to Michelin LT/AT2's, I lost 2mpg right away. I'm currently averaging about 14mpg. They were supposedly low rolling resistance. I guess not.

Have drivers changed? When my wife drives, she gets consistently 1-1.5mpg less than I do. I thought something was wrong with the truck, so I drove it for a few tanks and the mpg's went right back up. The kids say she drives the truck like a rocketship. LOL

Have you changed gas brands? Tire pressures ok?

I changed my plugs with MC SP515's. No change in mpg or performance from what I can tell. $8 each at OReilly's/Kragens.

For sure, stay away from Autolites. I tried their platinums in my old BMW and they were causing rough idle after about 10-15K. When I pulled them out, they were already worn!!

 

As I stated earlier the only thing I did to the truck was change the plugs to Champions, clean the K&N air filter, which was quite dirty but you would think both would increase mileage not decrease. Same drivers, gas, conditions, etc. I swapped out the air filter for a stock one just as a process of elimination but that wasn't it. Got new MC SP515 (OReillys @7.99ea) coming today. I'll change them on sunday and let you know the results.

 

best of luck and I will be waiting to hear the results. On my 05 after the plug change (using Motocraft) plugs both miles per gallon and power improved by 10%.

 

Haven't seen it mentioned yet but if you live in an area that has a "winter blend" for cold weather that may be making at least some of difference. People usually report a drop of 1-3 mpg in cold weather. Testing my new ecoboost to see if that is true, only thing is that I bought at end of October so may have to wait until spring to find out.

 

A friend at work has a 1994 F150 5.0L, he was getting 10-11 mpg, he finally listened to me and checked the plugs, PO had ACs in it. He installed MC plugs, 17-18 now.

 

Just a thought, but have you checked your mass airflow sensor? If some of that K&N oil got on your mass air flow sensor, it could be messing with the readings that is being sent to the computer causing the engine to run rich.

 

No I have not checked the mass airflow sensor. You are the second person to suggest this. I was told to get some CRC cleaner and clean it. I guess I'll try that before I change the plugs tomorrow it can't hurt to clean it anyway. As for the winter blend gas I do live in an area where they change the blends and I've noticed that can make quite a difference on some vehicles but I think the change was made before and I noticed the MPG loss the day after the plug (and air filter cleaning) change so I don't think that was it in this case. I'll give that cleaning a try today and let you know how I make out. Thanks for your thoughts.