No Tune-Ups for 100,000 Miles (Really?)

[RH77]

Introduction:
I temporarily traded cars with my Wife, who drives a lot more than I do (I'm home-based with a lower average miles/month on personal vehicles). This leaves me with the Integra or '06 TSX. If I need the car-seat I have to take the TSX to my local work location.

The Vehicle:
For a "near-luxury" compact/mid-sized sedan, the TSX was actually designed with economy and emissions in mind.

*Drag Co-Efficient of 0.27 (one of the lowest for '06)
*i-VTEC system, lowers emissions at idle
*Retains 4-cylinder engine for lighter weight
*Manu-matic "Sport Shift" offers more control over the transmission.

The Problem:
Over time, something has sapped FE. It used to pull-down low-to-mid 30's mixed average, but these days, we're lucky to get mid-to-high 20's.

Suspects:
*Foolishly replaced the front tires with higher rolling resistance "cheaper" alternatives
*Front partial undertray has deformed under heat, which has dropped into the wind-stream.
*It says "Premium Fuel Required", but...

Investigation/Advice/Preventative
Ok, back to the title of the thread. We're running at 75K miles with a recent quick change of the transmission fluid. New tires are coming up and the undertray is what it is. Oil changes at required intervals, Seafoam cleansing regularly (crank, tank, and brake booster line -- the neighbors love that one).

What I don't get -- no tune-ups for "100K miles". Is this typically the case, for real? If so, should I replace the plugs and packs sooner?

Premium Fuel -- I've given-up on the argument and run either mid-grade or premium. 87-Octane seems to elicit pinging.

Any recommendations?

Thanks Folks...

/RH77

[Big Dave]

At a hundred grand you may have some plug wires breaking down. Spark plugs pretty much last forever since tetraethyllead went away. Electronic ignitions don't wander like old-school distributors did., but underhood heat still breaks down insulation.

Check your brake pads. Everybody uses sintered metallic brakes these days. When iron rusts, it expands. You may have rust at the edge where the rotor doesn't wear off the soft, weak ryst and brakes may be dragging. Also re-lube the caliper slide pins. They get get dry and cause brakes to drag.

[Ryland]

I'm going to guess that if you replaced your spark plugs and used premium gasoline you are going to see your mileage clime back up, I'm not sure where Big Dave is getting the lack of spark plug wear from, but as I understand it spark plugs wear because of the electrical arcing wearing the tip down, at least that is what the SAE says in their paper on spark plugs and I've changed more then a hand full of spark plugs that were wore out, down to little nubs.
Your engine might not ping with lower grade gasoline but it will richen the fuel mix and adjust the timing to make up for it, chances are you will see a cost savings from better MPG that will out weight the increase in fuel cost and if not it will have cost you an extra 15 cents per gallon or around $2.00 right?

[Fat Charlie]

Lots of cars use platinum plugs. It sounds "luxury" and "performance" but it's really "economy." Most of them don't call for replacement until 90 or 100,000 and that's huge savings. I guess the factory sees the benefit in their reputation for reliability, so it's win-win. The ones in your car are probably due, though, and I blame the cheap gas. Messy detonations aren't good for anything involved, much less the only wear item in the chamber.

The first, cheapest and easiest step is to fix or remove the undertray. It's hurting you, so get down there with a drill and some zip ties. Take a look at your air filter. Don't make the same tire mistake this time, and pretty soon you'll be driving exactly what Honda wanted you to drive.

[mcguire]

My F150 is coming up on 100,000 miles, which is the first service interval that calls for replacement plugs. I swapped them out this last weekend and the old plugs looked to be in excellent shape with the exception that the gap had increased from the .052" (?) spec to about .06. I was duly impressed.

This engine calls for 87 octane, and I haven't notice any pinging, so I'm thinking there was no extra wear from detonation. It's also got coil-over-plug doo-dads, which seemed to be in fine shape externally.

I have noticed the mileage decreasing a bit over the last few thousand miles; if the normal service doesn't bring it back up I'll have to dig deeper, possibly starting with the coil packs (since they're easy to get to ).