Codeodd

Hi everyone, I was flipping through my mom's RX 330 pamphlets last night to see if there was anything else I didn't realize about the car.

Before, I didn't know there was a difference between 4 and D on the transmission shifter, but the pamphlet told me that there was a difference, and D had better gas mileage. Because the two are on the same vertical height, I think I've been driving in 4 instead of D. I'm not sure how much this affects mileage, but will driving in D be noticeably better? The past few fuel-ups have had 16MPG average (basically all city- not inner city, but suburban driving) and I'm not sure if that's normal or not.

Anyways, how much of a difference in fuel economy is there between shifting in 4 and D? This is really interesting to me.. cause I'd like to save some money! $$$

hypervish

Yes, there will be a fuel economy increase not so much in city though.

D means 5th gear, which is the second overdrive (4th being the first) in the U150 transmission.

neelnaik

Welcome to Club Lexus, Codeodd!
4 basically just limits the gears the transmission can use to 1-4 gears. D(rive) allows 1-5 gears. In the city, you usually aren't using 5th gear even when your in Drive. However, on the highway, allowing it use 5th gear will make a significant difference, as your engine rpms will be lower at the same speed in 5th rather than in 4th. In other words, at highway speeds, your engine doesn't have to work as hard to maintain that speed when it is in 5th gear vs 4th gear.

16mpg in the city is normal for an AWD RX330. You do not mention whether or not your mother's RX is AWD or FWD. However, mpg is highly dependent on driving style, so it can vary a lot.

My recommendation is to just use D, so the vehicle can use all 5 gears as it sees best. If you are unsure whether or not you are in D or in 4, look at the instrument cluster. The position of the gear selector will be back-lit.

Rainbird

This is an interesting forum posting and what can happen the MPG when driving in 4th gear vs. D.

https://www.clublexus.com/forums/rx-...50-crap-2.html

Codeodd

Thank you everyone for the information, and Rainbird for that informative yet funny read

It's an AWD, and we also use regular fuel even though the 2006 is suggested to use premium. My mom bought the car in a better (financially) time so right now it's a bit harder to justify paying more at the pump, even if it shows throughout the longevity of the car.

If it was my decision, in all honesty I wouldn't drive a luxury vehicle because I don't have a job or that much car experience... I shall enjoy this temporary passage of ownership of my mom's car for a while though

Thank you again!