Jlail

Hey guys,

Recently stepped down from an 08 6.4L Lariat CCLB to a 2015 3.5L Ecoboost XLT Sport. Just went over 63k miles and I’m thinking about replacing spark plugs and coils.

Any advice/recommendations?

jharmon203

My advice would be read the manual maintenance schedule. I don't think you need to replace these yet. 100k miles for plugs is usually the case. Coils only if there is an issue. Unless you are a guy who like the extreme preventative maintenance.

What advice and recommendations are you looking for? How to do this project? If you actually need to do it? Why are you thinking about replacing both of these? Are you having problems?

Jlail

I appreciate the quick reply. I guess I just want to do something to my truck this weekend. I’m looking for recommendations to improve performance/fuel economy. I’ve only been getting 11mpg in town and I don’t drive it like a race car.

chimmike

spark plugs are a great idea. Motorcraft or NGK Iridium only.
Other than that, I'd do the differential fluids, maybe a trans flush.

jharmon203

Again read your maintenance schedule in the manual. Have you hand calculated your MPG or are you using the estimated one on the dash? Things that MIGHT help your MPG improve would be changing your engine oil to fully synthetic, air filters, spark plugs, check your tire inflation (it needs to be at what is recommended for the truck, do not over inflate, it wont help) For spark plugs, match OEM quality.

I wouldn't recommend a trans flush unless the maintenance schedule recommends it. Check fluid levels though.

Spooled

Switching from a junk 6.4 to a 3.5 EB is definitely a step up, not down!

Napalm

How are you only getting 11 mpg - are you sure it's getting into overdrive? even in town once i get near 40-45 - I'll be in 5th which is an overdrive gear.

As far as plugs - do that. don't know you need the boots, but maybe. I would not buy the coils unless you have a CEL for misfires. the coils hold up well.. You might damage one in removal but I doubt it.


FLuids - if it's used but new to you. Coolant, diff and transfer case, and brake fluid flush.

Then I would take it to a dealer or quality shop and let them do the transmission fluid exchange. (big machine, tank o fluid - pulls out all the transmission fluid - puts in fresh)


and if the weather is nice in your area - wash and polish it.

sholxgt

Ditto the above! I'm only 3 days into ownership of my 3.5 truck, but I traded in a Lincoln MKS with the 3.5 EB. Same principles apply to both. These EB motors eat plugs. If on stock tune, 60k changes at max. If on a hot tune, 30k intervals. Mine at 30k in my tuned Lincoln were not pretty.

Ditto on the type of plugs as well. Hard to beat sticking with the OEM Motorcraft. If you don't want those for some reason, go with NGK iridiums.

tvsjr

I would do a complete fluid change on everything, unless you know for certain how the truck was treated previously.

Plugs should definitely be done - EBs eat plugs, tuned EBs *really* eat plugs. Coils aren't necessary unless you have a misfire issue.

Fatmattyd

I wouldn't listen to the owners manual only guys. 100k miles for plug changes is for marketing and sales.
Definitely the plugs (stick w/ motorcraft), and possibly the boot covers if you see any carbon tracing on the plugs. They are easy to do, but the electrical clip on the coil connector is a bit of a PITA.

I got my 2015 used as a CPO and did the front and rear diff fluids, the transfer case, and dropped the trans and changed the screen. Maybe overkill, sure. But it's my money and time.

The cabin air filter is a bit of a PITA too, but it's nice to know it's been done. The air filter's easy and cheap. Basic tune up stuff, especially given your mileage.

It might be worth trying to reset the transmissions learned settings. I'm not 100% sure how to do this, but I think others have mentioned disconnecting the battery for a short time.
The transmissions in these trucks have some sort of learning procedure. Would be nice to have it learn your driving style vs. the previous owner's.

If you do all this, and the mileage doesn't improve, post an update. Tons of helpful and knowledgeable folks on this forum who will probably have more & better ideas than me.

Good luck and enjoy your new rig!