lsft

I think it's up to the owner to decide what gas they prefer to put in. The manual does say both works. Some may prefer to use premium as a preventive measure based on the manual.

midcow3

Well, I guess one could quit driving as a preventative measure against automobile wrecks!

lsft

Again, that's up to the owner of the vehicle. Right?

Lex2000TL

Sorry, but you do not get your facts quite straight.
Premium gasoline has the same "thermal efficiency" as regular. The only difference is in the type (and quantity) of different additives. Some are added to keep your fuel system clean and the others to adjust octane number.
The octane number indicates gasoline ability to resist spontaneous and premature combustion / explosion from compression in cylinders.
Gas/ air mixture in cylinder does not burn instantly (like explosion), but over period of milliseconds, all while piston is moving down, past dead point which is a full compression. Low octane gas, if used in high-compression engine which is designed for high octane gas (premium), will explode and not burn in controlled process. If gas/air mixture does not burn but explodes (due to gas not resisting heat from compression), it will produce hard blow (aka knocking sound). Over time these “blows” will damage your engine bearings in crankshaft and wrist pin.

Use gasoline with octane number per car manual. Using gas with number higher vs stated in manual makes no impact on engine performance or gas mileage, and is waste of money.
If car manual state that "premium is required", use premium. If it says "premium is recommended", that means that the engine is designed to run on either and you can safely use regular gasoline. Of course, when using regular gas your can ECU will adjust timing to prevent "knocking". Adjusting timing results in slight power drop, but NO damage to the engine.

703

disagree on the A25A engine. As you can see from the BTE graph plotted over thousands of data points that the engine spends more time at higher thermal efficiency with Tier 2 fuel over the entire power and torque band.

With regards to what the different octane fuel is and isn’t. That’s not really the point I’m making and the general motherhood statements are fine for all intent and purposes. Not debating that at all.

what I’m highlighting here are the specificity of the fuel application to the engine in the NX350h.

Lex2000TL

What you see is not a gasoline efficiency difference but a difference in engine efficiency. As I mentioned, engine will adjust timing for regular, thus adjusting/loosing efficiency. Both gasolines have the same efficiency. Should you use premium or regular in engine that is designed for regular, you will not see a difference in "efficiency".

703

That’s what I’m referring to - BTE, brake thermal efficiency. The engine is more efficient at converting the same amount of fuel to mechanical energy when the fuel is Tier 2.

kingofire

Use regular fuel and use BG44K every 10,000 miles.

midcow3

It is all about entropy

Mrnovanova

I don't know if this helps but the car itself just says no E85 which is ethanol if I'm not mistaken. Anything above that is acceptable.

chuuck1e

So if 91 octane is way better than 87, then 100 would be the bomb, right? I filled up for the first time yesterday, and drove by a station that used to sell 100 octane racing gas from one of its pumps. They no longer did so, but did have 5 gallon containers of Sunoco Race Fuel for sale.

As I left that station, I saw that there was another station down the street that does sell racing fuel from one if its pumps. It was $9.95 per gallon, and did not indicate the octane rating, so I passed.

Kusala

I've never had any Shell V-Power premium petrol issues for my German cars. I will be continuing to use their premium fuel in the NX450H+ to avoid ethanol (despite the high cost in British Columbia). Ethanol is corrosive, and if you never burn fuel in the 450H+, you're asking for problems. As pointed out here by the Car Care Nut.

.

vincej

We compared seat of the pants differences between regular and premium in the Volvo XC90 3.2 L and noticed none. Perhaps we should have done some range tests to see if the car would go further on a tank of premium but we did not. So it has been regular fuel for years while the manual as I recall recommends premium.

I have also been told that premium fuels here do not have any ethanol, something else to consider.

Back in the seventies a few buddies and I did a trip to Mexico in a 64 Impala with a 283 engine. North of the border it ran fine on regular but in Mexico we couldn't use the cheaper Pemex grade without hearing the pinging.

Edit: In the winter of 77/78 I worked in Edmonton and one -40 day the 69 Fairlane 289 would not start, even after being plugged in and cranking over nicely. I used to fill up at a station called Discount Gas but for the rest of the winter I used premium from a name brand station and no more problems.

midcow3

You needed new points and plugs and have you timing adjusted. Cars have changed dramatically in the last 50 or so years and a lot of the timing is now electronically adjusted on the fly.

YMMV,
MidCow3

2023nx350

Awesome report! Plenty of data to support their findings.