Jetstar

Is premium gas really necessary? I noticed the compression ratio for the engine is 13:1.

Curryolla

I've always wondered if Premium is "worth it." The RX 450h is recommended to run on Premium. Looking at MY2015, it has the exact same compression ratio, bore x stroke as the MY2016 Toyota Highlander Hybrid. The Highlander is 4861 pounds and the RX is 4652 lbs. Now, the MY2015 RX (AWD hybrid) is rated at 30/28/30 mpg. The MY2016 Highlander is 27/28/28 mpg. Finally, in the official specification sheet for the Highlander Hybrid states " 87-octane unleaded (or higher) ", and the official specification sheet for the RXh states "Performance numbers achieved with 91-octane unleaded fuel". With that, it is up to you to decide. I am planning to testing 87, 89, 91/93 once I get my RX and see if (1) Performance decreases noticeably, (2) Fuel economy decrease (misses break even price), (3) Engine does not sound "happy" (AKA pinging or knocking). From what I've been reading, Premium does result in better MPG.
http://toyotanews.pressroom.toyota.c...duct+specs.htm
http://pressroom.lexus.com/releases/...duct+specs.htm
http://pressroom.lexus.com/releases/...duct+specs.htm

Jetstar

Premium gas may result in better gas mileage, but it is at an additional cost. I've always felt that regular gas is best to use if it doesn't result in pre-detonation (pinging). How ironic that Lexus would produce a hybrid to save on gas yet the engine requires higher cost premium gas. A few years ago a study was released that confirmed my belief that premium gas does not give better gas mileage than regular gas unless it eliminates pinging.

VinceCL

Quite often engnes wth mid grade or premium fuel requirements will run fine on lower grades but a drop in mileage or reduction in drivability may result as the engine alters various variables to keep operating within a safe range (no pre-ignition/pinging and so forth). Timing is often adjusted by the computer to keep things running well. Forced induction vehicles can be very sensitive to lower grade fuels (my own experience included) and while it may run fine fuel efficiency can drop to a point that it might end up costing more money in the long run to buy the cheaper gas.

Also remember that hybrids are not about saving money on gas (though that can be a nice perk) they are about burning less of it.

Happy motoring

coolsaber

I guess since the hybrid does not really use the IC motor alot, gas tends to sit longer in the tank then say the 350. Due to that, maybe better gasoline quality is required? Who knows for sure?

TexasRxh

I'm guessing that unless you drive the same miles every day in similar weather and use the same driving habits it would be difficult to compare mileage based on gasoline grade.

This is my 3rd Rxh vehicle so my driving habits changed over the years and are fairly well set: I've learned to drive "more hybrid friendly" (avoiding rabbit starts, accelerate as easily as practical). It's actually a more pleasant driving experience. I've posted the mileage from my first few fill-ups and, I must say, I'm impressed with the increased mpg I'm getting from the 16 Rxh versus my 13 Rxh. My driving habits did not change but the mileage is about 15% better (from 28-ish to 32-ish). So I am definitely a happy camper!

Curryolla

I'll admit, it won't be a perfect test, but I did some similar tests with my Infiniti and found it ran well enough on 87. My commute is mostly highway, 200-400 miles, across either Ohio and Indiana or Ohio and Pennsylvania. My driving habits are fairly consistent, expcially using cruise control. Unfortunately, there is no way to control the weather , but I'll try my best to keep the air conditioning off and use the same drive mode. I'm just curious if the gas type will effect the way the car feels.

I'll report results, and look forward to seeing what happens. Suggestions are more than welcome!

Macs4RX

Member dfc350 posted a while back about Top-Tier, which is an organization that helps ensure the gas meets certain specifications, especially regarding additives. Members (like Shell, Exxon, etc.) must demonstrate compliance to these fuel standards. I read somewhere that some store brands, although they must meet federal additive concentrations, have a lower concentration of additives than some Top-Tier members. Apparently, the all important additives are introduced into the bulk gas at the local/regional terminal then transported by truck to the member gas stations (the gas stations themselves also need to be compliant with Top-Tier guidelines). Our RX owners manual does recommend using a Top-Tier certified gas retailer although I'm sorry to say I can't find where I read that. I've been using a store brand gas for my RX350 but am going to switch to a Top-Tier gas retailer for my next and subsequent refueling.

TexasRxh

Yeah, I pretty much stick to Top-Tier retailers if for no other reason than I "feel" like I'm more likely to get "good" gasoline with no water or other contaminants due to franchising requirements from the majors.

kitlz

On the second tank now and still averaging 30 MPG during short hilly commutes. Over the weekend it did go up to 32 on a longer drive. I have a feeling topping my all time best of 36 is very possible. Getting higher numbers seems so effortless. I also stick with top tier brand Shell, 93 octane. Never had a problem. Plus I receive a $.10-.30 discount per gallon through one of the local supermarkets when I present their card at fill-up.

ericsan13

The best I can get is 27MPG with a 10 mile round-trip commute. Same MPG with 250+ mile roadtrips. Are you staying in ECO? Max speed <70mph? I just cannot recreate the numbers no matter what I try.

TexasRxh

Check out the mileage thread and you'll see that my '13 Rxh averaged ~ 28.5 over the 3.5 years I had it. My driving habits did not change when I got the '16 Rxh in April but my MPGs went to almost 32. I noticed that my 3Rxh would not let me stay in EV mode if speed exceeded 25 mph but I've had the 4Rxh up to 35 still in EV mode. I suspect the electric motors are playing a more active role somehow.

kitlz

Eric, I'm in eco mode. Basically the same commute as you with half of it hills. Speed is 40 MPH or lower. I can still manage 30 MPG. My driving style is the same (read slightly spirited). And it does stay in EV mode longer like John said.

I'm not trying to derail the thread. Just more to demonstrate what kind of mileage I'm getting using what it says in the manual (91 octane or higher). Same gas, same commute in the '10, I was seeing around 26-27 MPG. Makes me wonder what kind of tweaks or improvements were made on the 4RXh.

TexasRxh

And BTW I drive in Normal mode all the time.

gadgetman1

I just averaged 27 mpg driving thru hills at 75-80 mph for about 200 miles. I filled the tank with 93 & when I got home the gas gauge read a little less than 3/4 of a tank. I'm very impressed with this RX 450h so far.