Highway mileage not quite optimal

[aroundawhile]

I owned a 99 Solara that I replaced with a 2000 Camry. (Elderly neighbor owned it, 98K miles in 10 years, cleanest used vehicle I've ever purchased).

I regularly take a 700 mile weekend round trip. The Solara would regularly hit 28 mpg and sometimes as much as 29.5 on this trip. The four door Camry never gets above 26.5....both are V6's.

Prior owner of the four door gave me all the records. I don't see that the plugs have ever been replaced, although I pulled one and it appeared to be in good condition. I ran a can of Seafoam through the tank to help clean the injectors. The air filter is new and there are no codes thrown (I monitor the temps and whatnot using a Scanguage II full time). I cleaned the throttle body not too long ago.

Now, I know I'm obsessing over a minor issue, but I would think that the mileage would be similar. The four door has a slightly higher profile, and probably weighs a little more, but the mileage is almost a 10% differential?

I don't mind spending $ to maintain a vehicle, so a plug replacement would probably be in order. I'm not a fan of replacing oxygen sensors until they go bad and start throwing codes. Is there anything simple I'm overlooking here?

[fenixus]

change the plugs first if they weren't touched ever. but even before you do that run the sea foam treatment.

was the timing belt changed at 90k miles or not yet? it's due.

I would also flush all fluids including brakes and cooling.

your Solara likely was California emission specs (I think all sold in US market are) so it was using longer lasting AFR sensors for the upstream.

Possible that your Camry is federal emission specs? if yes, then it uses cheaper (and less precise and shorter lasting) Heated o2 sensors in upstream. maybe they are on the way out?

If nothing helps I would replace them along with the o2 sensor under car (post-cat). those narrow band thingies do not like running much over 100k miles. AFR can last a bit longer (120-150k), but they surely loose some precision at such mileage even before going bad.

other than that, check the brakes for slight dragging.

[BamZipPow]

Tire pressures and type are another consideration. What kinda rims are on there?

Keep in mind that even though the Solara and Camry are close in shapes...they do differ in weight (2 door vs 4 door).

[aroundawhile]

Thanks for the input. Prior Owner did have the timing belt/water pump/ Seals done. I have already run the Seaform through the tank. Didn't appear to help (although it could not have hurt...). Tire air pressure is regularly checked and never below 32. One trip I increased it to 35 to see if there was a difference. Didn't make a difference on MPG that I could tell, but the ride was a little more harsh.

I will do the plug replacement first. As I stated earlier I'm not a big fan of the oxygen sensor replacement as a PM issue, I tend to just react when those start throwing codes.

The cost/benefit payback on the plug replacement is only about 2K miles so that is a no brainer....I'd have to price the sensors to make the determination there, but I suspect the parts are somewhat $pendy.

[fenixus]

^not at all.

if you have Advance Auto Parts around you, you can order online 6 OEM Denso Double Platinum (PK20TR11) spark plugs with a discount code BIG15 ($15 off $40) and the total will be close to $28+tax, local pickup after 1 hour

For AFR sensors, I usually check part numbers on Denso Afetrmarket website here:
http://www.densoaftermarket.com/catalog/

and then look for genuine Denso sensors on ebay and amazon, that's where they usually come up cheapest for me, around $107/each shipped free.

The post-cat sensor (also Denso OE) is cheaper and pricing vary, sometimes I was able to get it as cheap as $40 shipped, other times around $77.

Hope it helps.

P.S.
for me driving on 35psi tires was giving me as well minimal MPG increase for the cost of increased ride harshness, so now me too sticking to 32-33psi at cold tire pressure and it seems nice.

[pmesfun]

There isn't an AAP store in DFW, but if you need spark plugs, Toyota of Dallas is the cheapest for parts if you order online then pick it up. $7 per plug.
PK20TR11
PN#9091901194
http://www.toyotapartsales.com/partl...?siteid=214074