So my wife and I recently picked up an 02 3.3l caravan @ 89k miles. We normally net close to the "HWY" ratings in all of our vehicles because we live out in the country so the driving is more HWY than city style.

We've been getting 18-20mpg despite the following attempts to get closer to the 24mpg mark;

New air filter
5w-30 synthetic blend oil
Relatively new Plugs/wires.
No CEL codes.
Checked and evened out tire pressure.
Kept acceleration at a low; smooth driving as usual.

Now a few questions:

I've read here twice about 5w-20 being the factory recommended oil; where is anyone reading this? My manual states 5w-30. Which weight should I use? I'd imagine I may do better with fully synthetic 5w-20 due to its lighter weight.

The factory specifications only require 87 Octane correct? Is there a decent increase in gas mileage/performance worth stepping up to 89 or 91/93 octane and paying the higher price?

My tires are 215/70/15 on the factory steels. Is this a good tire size? Are the factory rims lighter than the steels? I'm wondering if perhaps the brand tire I have is part of the culprit too as I've read online.

Other than fuel injector cleaner (which I probably should do ASAP the van sat for a while before I bought it), is there anything else to cover? Do you guys ever replace the PCV valve?

Lastly; how important is it to have the spark plugs gapped correctly? Will that drastically affect gas mileage or just power? the factory setting is .05 I believe which looks smaller than mine are set at.

I'm new to this forum and this is my first post so Hello!

 

I don't think your tire size is correct. i thought they are suppose to be 215/65/15

have you verified that the speedometer and odometer are absolutely accurate?

why don't you just do a complete and proper tune up with correct gap.

only use recommended oil viscosity.

higher octane won't have much affect on fuel mileage.

idk that the pcv would have any effect on your fuel mileage issue but if it makes you more at ease, put a new one in but only use an OEM dealer unit. i read to many aftermarket ones causing problems.

 

mine is an 06
it says it on the oil cap and in the manual for 5w-20, I switched to full synthetic oil at 60k miles

with that being said I have a v6 3.8l I get about 24 on the highway and around 14-15 in my heavy stopping, usually I ave 18.5-19.5mpg over all

and I notice that the 24mpg only will stay 24 if you will keep your speed very steady for and have very little slow downs, slowing down and going kills the mpg, in fact on a straight (clear) stretch of highway if i reset the computer, I get around 29mpg, but as soon as you slow for a slower car or switch lanes and pass it drops down quickly, if you can keep cruise control on the whole time you should get that higher mpg, but it is hard with current traffic on roads

 

I tried synthetic oil, it ran out my oil pan. I had to switch back to conventional. I have '99 and still get 19 to 23 miles depending on highway or city. I agree that a consistent speed is a good idea since you drive highway like miles. I also took out my 3rd row since in my case I rarely use it.

 

Look for a possible O2 sensor. My van ran great, But got lousy mileage because of a failing (not dead yet) O2 sensor. Upstream.
Get the van in Overdrive ASAP. Anything over 33mph can be done in OD.
So you have to reach 40 and slow down around town. Learn to let the van roll more.
Consider upping tire pressure. Towards max pressure stamped on tires helps. Tires wear just fine.
Taking off the roof rack crossovers. It didn't make a big mileage change. But the trip got quieter.
I played with Mobil 1. Couldn't confirm a 1 mpg increase. So I returned to regular oil.

If you have the overhead instant MPG monitor, Use it. It's a great teacher.
I regularly get about 24 mpg on highway. 19 city.
My wife gets 14.5 mpg city. So style of driving matters a lot.

Good Luck

 

ok, a few things. i also have a 2002 caravan with the 3.3L. it sits on 215/70/15 on the factory steels, and it is what the door jamb calls for. engine oil cap and owners manual calls for 5w 30. it also calls for 87 octain fuel, and says any higher octanes may cause poorer performance. i dont know my exact mileage per gallon, but at 121,430 i obtain roughly 250 miles on 11 gallons or a fuzz over 22 MPG city. i do not have cruise control. i have my luggage cross bars in place, but i do have them in the recommended setting for efficiency. if you look at the rack part attached to the roof there are two arrows, one front and one rear. place the cross bars in these locations for optimum airflow. i dont want to take mine off cause ive had a few times when the wife and i went out not expecting to buy anything and found something that wouldnt fit in the van. i learned to always carry ratchet straps also.