Mpg On The Awd 300?

mckellyb · August 10, 2003

Took our first long, relaxed trip, yesterday, and while the RX had about 80 miles of 17.8 MPG on it, I managed to coax it up to 20.9 on the entire tank before hitting "E". Well, the needle is below "E", but I like to know *exactly* how much run time I have, in case I'm ever in a situation I need to make a walk/don't walk decision.

So, it looks like being gentle, yet with the AC on, on rolling hills highways will get you right about the 22 MPG EPA figure, but are you guys/girls seeing more/less on average. My wife drives it almost exclusively in-town, so I don't expect to see the 18 city figure, as avg. speeds tend to be sub-30 MPH.

Thanks

jbrooksbreeden · August 10, 2003

I'm getting about 21.7 average for road and around town.

b.

jeremyp · August 11, 2003

I reset the mpg last week and have been averaging 18.3 so far since. It was at 19.4. This is probrably due to the fact that I've had the A/C on continuously because of the heat and humidity around here lately.

tmastres · August 12, 2003

I've got the exact same vehicle and I just managed 23.0 on a 220 mile trip of exclusively highway miles w/ the a/c on and NO cruise control. Ironically a similar trip taken two weeks prior netted only 22.3 when using cruise control the vast majority of the time. I usually cruise at 65-70 when working the throttle myself and generally set the cruise at 70 when using that. This is all with 89 octane gas if that makes any difference

mckellyb · August 15, 2003

Thanks for the info. Yeah, I've found cruise control is really only truly useful on roads like I-10 in New Mexico, as it can't anticipate hills, or if a person just *can't* hold a constant speed. Worse, on our Dodge Intrepid, it'll downshift to keep speed down, when going downhill, if you exceed the set speed by like, 3 mph. Aggrivating.

I'd bet, if I'd reset my MPG readout before the trip, it would have been about 22. Wait, I can figure it out. I was on 87 octane, FWIW. Have you noticed any diff between 87 and 89? The 3.5L motor in our Intrepid is ultra-picky about octane, and using 87, they recommend 89, allowed enough hesitation to kill the transmission mount log before its time. I've learned....

Let's see, my trip MPG was...22.23. This is rough, as I think that tank had 80 miles of 17.6 on it, and we took about a 220 mile trip, which at the end, showed an MPG figure of 21.0.

I did find, as we have 'full serve' *only* here in the People's Republic of Oregon, the first 'click off' of the fuel pump leaves room for about 2.5 more gallons. Yeah, gasoline needs some expansion room, but that's about 2 gallons of overkill, IMO. My Suzuki (yeah, we have three cars, can't get rid of this one, the Zuk) shuts off when there is .5 gallons of room left. Pefect, IMHO.

tmastres · August 15, 2003

This does shift the thread a bit but in response to the question of octane, I got used ot using 89 in my Dodge Dakota ( which would knock like heck with 87 ) so I just naturally began to use it in the Rx300. I had heard you could use 87 no problem but looking though some old posts I see some people recommend the 91 or 92. I've only used the 89 so far but I will try something different for the nex tank or two and let you know. ;)

mckellyb · August 18, 2003

Hey, thanks for looking into this! Best way to do it, as you're not likely to be able to tell, seat of the pants, is to watch your MPG figures on both 87 and 89 to see if there is a significant difference. By significant, I mean one MPG, or more.

Shockingly, unlike any other car I've been in, the Intrepid with the 3.5L motor, it's *obvious* it's retarding the timing off-idle, as you can feel the hesitation. 89 octane makes it go away. The Lexus is so freakin' smooth, however, I can't tell.

I was driving the RX, yesterday, on what used to be called a 'Sunday drive', just cruising around the countryside, and *man*, this car is **smoooottthhhh*. Even WOT shifts from 1st to 2nd are downright gentle. Blows my mind.

Sorry, back on topic...

Unlike your Dakota, the RX has at least one knock sensor, so even on Pemex, you wouldn't ever hear a knock/ping, the computer would keep retarding the timing 'till it produced almost no power, most likely.

With fuel prices here in the Portland, OR area increasing close to $.30 in the past 10 days, I'm gonna stick with 'regular' unleaded, 87 octane, for now. Regular is anywhere from $1.85 to $1.979, depending. *But* you don't have to get out an pump it for yourself!!! Instead, you get to sit in your car for 15 minutes and suck in the fumes.... :rolleyes: :angry: