Regular Or Premium Gas?

[ptyork]

Just to beat a dead horse, based on the assurances in this thread (and the gas shortages here in Georgia), I just put a half a tank of 87 octane on top of the gallon or so of 93 left in my 06 GS300. There haven't been any "problems" so far, but the power loss is quite noticeable. It feels like a drop of 20 hp at least. Yeah, like I'm a human dyno--but it feels like a 10% to 15% drop across the board from a sluggish take-off to mid-band acceleration. Based on this I'm expecting lower mileage, but I'll report on this in a couple of days (I have a pretty set driving pattern and get very consistent mileage). It may not be worse since I'm not one to push the car at all (might as well be driving a Civic these days) and I don't have a ton of stop and go, but it sure seems like it could be worse for someone bound and determined to get up to speed as quickly as possible. We'll see. Regardless, though, I'm definitely going back to premium next time I fill up...assuming that occurs at a station that actually has some...

[Lexus GS430 Guzzler]

I use Premium. It doesn't matter to me...I used to drive a Shelby GT earlier this year.

With regular 87 gasoline, I notice a reduction in horsepower and the drive is rougher. With the 91 it's much stronger, smoother, and I crank out just a little more miles with 91. So in the end, it's all kinda the same to me.

[themntneer]

I disagree that Lexus would advertise the fact that the car runs just fine on regular.

I disagree, because I have seen it happen. Maybe not Lexus "corporate" but Lexus "salespeople" will tell customers that they can use regular unleaded to make the sale. Most people buying cars don't frequent these types of forums so they are not privy to these types of conversations. Many consumers don't go into the physics of octane rating, they just know that if the book says you got to use premium and premium gas is 20¢ to 40¢ more expensive per gallon, then they may tend towards a high end vehicle that does not "recommend" premium. Now, if the salesman says, "you can use regular if you have to, the engine will compensate" then the sale is most always made.

As for "Lexus recommended brand oil"..........DO NOT GET ME STARTED ON THIS TOPIC AS IT IS A BEATEN HORSE. use the search function and look for a member named "monarch". DON"T GO THERE!!!!

Tranny fluid is a different story, I agree there, use Toyota T-IV or WS if it calls for it.

steviej

As for premium or regular, we have found that using a higher grade gas gives you better gas mileage, which in the long run makes it more economical. We have tried this "experiment" on each car we've owned and it does make a difference, even on an average run of the mill make and model. But, don't take my word for it.....try it yourself.

[Angelo M]

On 6/23/2008 at 10:06 PM, steviej said:

On 6/25/2008 at 4:12 PM, madyash said:

Not sure I agree with you. I read that the Lexus recommended oil and transmission fluid are better than other stuff (part of the reason they only ask for oil changes every 5K miles). There is conclusive evidence of the fact that going with cheaper oils will damage the car and so I would never do that. There is NOT conclusive evidence that regular gas will damage the car, so it's not the same.

I certainly agree that some articles talk about people putting premium in cars that require regular and how that has no benefit. However the articles I'm talking about specfically refer to cars that "require" premium but work just fine on regular. Note, not ALL cars that require premium will do fine with regular - there are always exceptions. As confirmed by Lexus techs, the computers in the GS (and most new cars) will adjust for a lower grade gas so as to not damage the vehicle due to pinging or knocking. You're certainly right about higher compression engines needed higher octanes to burn properly, but the computer will adjust for the combination of high compression and lower octane. Though "premium" is required for the performance to match the specs, regular will not cause any harm - a marginal lack in performance, yes, but no harm.

I disagree that Lexus would advertise the fact that the car runs just fine on regular. This is for two reasons: 1) doing so would require it to drop down the performance numbers a bit since they can't be achieved with regular, and 2) it would be damaging to consumer pride. Folks can deny all they want, but psychology is certainly involved. Generally, drivers who buy 50K cars expect their high end cars to take high end fuel. I'm sure the rising gas prices are changing that psychology, which is part of the reason this thread exists. Would we have been debating this when gas was $1.50/gallon?

I used to street race and I can tell you from experience and first hand knowledge of tuning engines that there are a lot of stupid myths about octane base entirely on "bro science". I'm here to put it all to rest. First of all, ALL GASOLINE HAS THE SAME AMOUNT OF ENERGY!!! So that means that anything greater than the minimum recommended by the owner's manual is just a waste of money. So if the owner's manual says just to use 87, just use 87. Anything higher will not do anything special for the car. Second thing: OCTANE MEANS RESISTANCE TO COMBUSTION. This means that the octane level will indicate how smooth the gas will ignite as a single explosion in the cylinder. Higher compressions may cause multiple explosions in the cylinder when it only need 1. So that means if a vehicle says "Premium Required" or the owner's manual recommends 89 or 91 or higher, DO NOT USE ANYTHING LOWER THAN WHAT IT SAYS. This is most common with cars equipped with Turbo(s). Using a fuel lower than what the owner's manual says may cause engine knocking and may damage the car. And this goes for all driving and traveling situations. Lexus equips their engines with fuel sensors to adapt to climate and temperature. So just stick with what the owner's manual says. NEVER USE ANYTHING LOWER THAN 87 ON ANY LEXUS EVER!!! Last thing: Some of Lexus's cars say "Premium Recommended". In this case, you can select which grade you wish to use. This is more common with the larger engines (Usually V6 or larger). If it says "Premium Recommended", this means that 87 will be fine, but the the engine has a fuel sensor that can switch up the compression for higher performance if it senses higher Octane Fuel (89 or above). In such a case, my rule of thumb is to just use 87 (or whatever is the lowest octane rating recommended by the owner's manual) for common daily driving, and high octane 91 for performance racetrack driving or highway long distance traveling. Key thing to remember for "Premium Recommended" is that daily driving will burn all gas the same most of the time, and high octane will give you more horse power for performance driving or more MPG for long distance road trips. Other than that, just make sure you are always filling up with Top Tier gas to make cure you don't get carbon build up since that'll increase the compression over time. HOPE THIS HELPS! CHEERS!

If you're concerned about ethanol: Again: READ THE OWNER'S MANUAL!! But if you lost your manual, you can just find it online. But if you still cant find your owner's manual online, here is a rule of thumb: Model Year 1999 and older should use Ethanol-Free gas. Model years 2000 to 2013 should not use any gas with ethanol higher than 10% unless its specified to be Flex Fuel. Model years 2013 and should not use any gas with anything higher than 15% ethanol unless specified as a Flex Fuel. Flex Fuel vehicles can use any gas up to 85% ethanol.

 

[CowBoE]

2/3 of the time I use regular, but do periodically use premium. 

I also use Lucas fuel additive about once a quarter and do seafoam cleaning once a year. 

I have not notice any much power loss or engine knocking with regular.