Premium?

[Poisson]

There's a thread over at the Mercedes forum where the consensus is that using the highest possible octane fuel will result in smoother running, more power and better economy. Any comments in relation to the RX350?

[Losiho]

I don't use anything other than 98 octane. Either Caltex Vortex 98 (preferred) or BP 98 (sluggish throttle response with this fuel).

I'll never use Ethanol, even though Lexus say it's ok to use.......

[Poisson]

I don't use anything other than 98 octane. Either Caltex Vortex 98 (preferred) or BP 98 (sluggish throttle response with this fuel).

I'll never use Ethanol, even though Lexus say it's ok to use.......

G'day Losiho. Have you done any comparative testing between the various grades? I'd really like to hear if somebody has tried both 91 and 98 octane and quantified the difference. Lexus say the engine is designed for 91 octane, so why spend an extra 12c/litre unless it actually does make a measurable difference?

[DANSLEX]

Regardless whether designed for 91 or not, you will get better mileage out of 98 simply due to higher octane rating. There will be less petrol used up as 98 has more energy than 91.

I haven't tried it on my IS, but few years ago when I put 91 into my soarer, which I always ran on 98, it used up noticeably more fuel.

Also, premium fuel is more refined and cleaner for the engine.

[Losiho]

As Danslex said, you always get better fuel economy with premium. I always record my fuel consumption figures every tank for every car I've owned (since 1993) and this has always been confirmed, not just with Lexus.

There is also a subtle, but noticeable (to me) difference between the 98 octane brands. As I said, I prefer Caltex 98, simply because it has the throttle response I enjoy. I can notice the sluggish throttle response with BP almost as soon as I fill up with it (about 50km later). But, on the flipside, you get slightly better fuel economy with BP compared with Caltex.

I'll never use Shell V Power - terrible throttle response, crap performance, but good fuel economy.

There isn't a Mobil servo within cooee of my "normal route", so I never get to try Synergy 8000.

Btw, are you sure Lexus say 91 octane is ok to use ? I'm pretty sure my RX350 owner's manual says "at least 95 octane".

[Poisson]

Btw, are you sure Lexus say 91 octane is ok to use ? I'm pretty sure my RX350 owner's manual says "at least 95 octane".

You made me think... on re-checking the manual (mine's a 2006 model) it does say at least 91 octane, but 95 is recommended "for better performance". I'll have to give it a try and see. We don't have 98 octane Shell around here, and the BP is always more expensive than the others, so ll give the Caltex a go.

[fleetmanager]

Btw, are you sure Lexus say 91 octane is ok to use ? I'm pretty sure my RX350 owner's manual says "at least 95 octane".

You made me think... on re-checking the manual (mine's a 2006 model) it does say at least 91 octane, but 95 is recommended "for better performance". I'll have to give it a try and see. We don't have 98 octane Shell around here, and the BP is always morer expensive thatn the others, so ll give the Caltex a go.

Loshio I have no doubt that you are getting better fuel efficiency but how much?? I have tried all 3 (91, 98 & E10) and I notice very little difference in efficency. On my last road trip Melbourne to Bega I got about 60klms less on E10 when the vehicle was running at 8.4L/100, I was getting 630-660 out of a tank. This was just cruising speed with the odd firm foot plant to get past the caravan conveys... I have previously tried 98 and I got all of 80klms further.... At an extra 12cpl in my opinion it wasn't worth it. Different horses for different courses and if you have the money and you want to spend it go for it.

For what it is worth I manage 1400 vehicles, most LC's and my account with Caltex is 450K p/m, anytime I talk to them about high octane fuels they grin from ear to ear.... I am sure they would be happy to see an extra couple of G's in my invoice each month.

Cheers,

[Losiho]

My trip from home to work each day is exactly 5km (each way). Do the math......1855 kilogram 4WD doing short distances = I'm never going to get great fuel economy, no matter what fuel I use.

Don't get me started on any ethanol blend fuel. Sugar belongs in my tea/coffee cup, not in my petrol tank . The sugar industry should stay the hell out of the motor industry.

If an owner's manual says "at least 95 octane" or "premium preferred", I don't see the "economy" of using 91 octane.

[Poisson]

By coincidence there was an article in this morning's West by Peter Fitzpatrick (MTA director) who made a couple of interesting points:

1. The differential between regular and premium has grown from 4c/L to around 9 - 12c/L over the past couple of years
   
2. The differential is generally higher in the eastern states than here in WA
   
3. As a rule of thumb, each increase of 1 RON will give you a 1% increase in efficiency or power. How you drive will determine which you get.
   

So if efficiency is your goal, going from 91 to 98 octane will give you approx 7% increase - but it might cost you more than 7% at the pump.

[Fuzzielogic]

For stop-start driving in traffic theres not that much benefit using premium compared to E10, but for a long distance trip I prefer a higher octane fuel.

[Poisson]

I tried a tank of 95 octane, with negligible difference in either economy or performance (all round town driving). The engine seemed to run a tiny bit smoother, but that could equally be wishful thinking. Given the extra cost of 98 (14c/l more than 91) I don't think I'll bother with that. I'll give the 95 another go next time I do a country run, but for round town it's not worth the extra cost.

[Lexo]

If an owner's manual says "at least 95 octane" or "premium preferred", I don't see the "economy" of using 91 octane.

To my surprise, the user manual on my RX400H says 'at least 95 octane or higher'. I'm pretty sure I read somewhere before I bought my RX400h that the RX Hybrid with the 3.3L engine requires 91 unleaded whereas the RX350 requires a minimum of 95 octane. I don't plan on using anything other than 95, preferably Carltex Vortex.

[aussieguy1]

I opt for premium unleaded, but I've got a work fuel card that pays my fuel bills.

From the many arguments I've read regarding different fuel grades, premium advocates argue that you get better performance, more kms from a full tank & generally better for your car's engine.

Cons are that premium is almost 10~12cents more expensive per litre (approx $8~9 more expensive per tank).

I'd be interested to see if there's concrete data for whether or not E10/regular unleaded damages the engine or not.

[Jon_Zee]

On 10/2/2009 at 6:51 PM, Losiho said:

As Danslex said, you always get better fuel economy with premium. I always record my fuel consumption figures every tank for every car I've owned (since 1993) and this has always been confirmed, not just with Lexus.

There is also a subtle, but noticeable (to me) difference between the 98 octane brands. As I said, I prefer Caltex 98, simply because it has the throttle response I enjoy. I can notice the sluggish throttle response with BP almost as soon as I fill up with it (about 50km later). But, on the flipside, you get slightly better fuel economy with BP compared with Caltex.

I'll never use Shell V Power - terrible throttle response, crap performance, but good fuel economy.

There isn't a Mobil servo within cooee of my "normal route", so I never get to try Synergy 8000.

Btw, are you sure Lexus say 91 octane is ok to use ? I'm pretty sure my RX350 owner's manual says "at least 95 octane".

On the internet you will always see 91 for RX, but that's US 91. For Australians, we need at least 95RON.