My 4Runner definitely has more of a response to it in with premium. My manual states for optimal performance, use "premium" but you can use reg. All three of our other vehicles say to use regular.

 

Ram recommends 89 midgrade, i ran two tanks of regular 87 to test and it definately runs better on 89

 

Do you have the 5.7?

 

yes the 5.7 V8

 

Cool. I read that the Hemi 5.7 is EPA tested at 89 mid grade. So was just wondering.

 

Not about saving it but wasting it. Again over one million miles driven on regular with cars that premium is recommended not required (big difference) and zero engine problems and zero difference in gas mileage or performance. Under those conditions and experts advice paying $.70 more per gallon is a complete waste.

 

So I actually looked at the owner's manual for something specific. In the IS's owner's manual, the text is very clear that using less than 91 with either of the available engines may cause damage. However, such a warning doesn't exist within the pages of the previous-gen RX's manual. Instead, all we see is this:

However, in the current-gen (2019) model's manual, Lexus are very explicit that engine damage may occur. Just to be sure I'm not making this up, here is the link: https://drivers.lexus.com/t3Portal/d...f/OM0E065U.pdf

And a screenshot for convenience:


If I owned a car with such a warning (actually, I do), I'd never go below 91, unless there was an emergency. Now, perhaps it's really not necessary to use 91, especially considering this is a hybrid, making it easy to keep the revs down outside of sudden acceleration. However, if anything mentioning engine damage comes up, I am going to stay far away from that possibility.

 

No one anywhere has said there would be ‘engine problems’ using regular when premium is only recommended. I don’t think that’s ever been the case except 30+ years ago for cars that required premium.

as for zero difference in performance, maybe so for you, and maybe you drive gently, but obviously that isn’t everyone’s experience. So the premium cost may be ‘wasted’ on you, but it isn’t wasted on others. But certainly the premium (ha) that gas companies charge for premium is ridiculous, but i’ve got more important things to be concerned about than a few dollars every couple of weeks which if i choose to ‘save’ would make my car less responsive.

 

Interesting.

In my 2010 RX450h manual, it says (I'm paraphrasing here): "Use 91, but if it's not available, then use 87."

I did spend a few minutes looking up the 2019 Toyota Highlander Hybrid manual. Same engine model as in the RX450h, but they say to use 87. So the next step I guess is to see if there is an official engine timing spec, and if so, if the Lexus timing is more advanced.

I have an old '69 Vette with a 427 engine, and I am VERY familiar with the sound of low octane. Some guys even go to the local airport to buy 100LL aviation gasoline, which is a whole different animal from 91.

I am curious to get an official answer from Toyota. Or at least I can talk to a local certified Toyota mechanic who works on both cars and hear what he says.

 

Oddly enough, Toyota lists the Highlander Hybrid engine with a compression ratio of 12.5:1 and the RX450h at 13.0:1. Not much of a difference, but I had thought they would be the same.

 

I would be very interested to know more about the engine timing.

 

Don't want to sound condescending, but, in a nutshell, spark-timing is defined as difference in the crank-shaft angle between where the piston/connecting rod reaches top dead center (TDC) on the way up the compression-stroke and the moment that the spark plug fires (a few engines have more than one spark plug per cylinder, but it is not the norm). All else equal (heat, fuel-mixture, etc...), advanced timing (where the spark fires before TDC) gives more power, better throttle response, and, in some cases, better mileage, but produces more emissions from incompletely burned fuel and causes the engine to have more of a tendency to have ping and spark-knock from low-octane fuel. Retarded timing, in contrast, will give better emissions, a cleaner exhaust, and less of a tendency to ping from low-octane, but will lower power output, make for a more sluggish throttle response, and sometimes cause lower gas mileage.

Back in the 1970s, before the days of computer engine-controls, timing was retarded (and fuel-mixtures leaned) to help emissions, which made many engines sluggish. The advent of computerized engine functions, of course, meant that today's engines can be precisely-monitored by the split-second to give the best combination of power/efficiency/emissions.

 

Well, I'm probably not telling many of you on Car Chat what you don't already know (or have figured out)...and, if that's the case, feel free to skip on to the next thread. But, for those of you who are new to the world of vehicle-ownership, and/or don't have a lot of experience actually paying the bills (maybe some of you younger people are still at home, riding in or driving your parents' vehicles), economic reality will eventually come. When it comes time to start paying the bills, what you put into your gas tank, where you buy it, and any discounts along with it, especially over time, can make a real difference.

Don't get me wrong. I have long believed the old axiom (which, IMO, still applies today) that if one can afford a vehicle, he or she can afford to keep it filled up. But that is no excuse to be careless or waste money while doing so. A significant waste, at least IMO, is when vehicle owners use expensive premium fuel when it is not actually required, and much less expensive 87-Octane regular will do fine. Due to the way engine-computers are programmed today, the engine will make perhaps a few extra horses or foot-pounds of torque with the premium fuel (because the computer advances the spark-timing a little), but it is usually marginal, and most drivers will never notice the difference in normal driving. What you WILL notice (often big-time) is the large difference in price between 87 Octane regular and higher-octane gas. Unless you are experiencing spark-knock/ping in the engine, which will sound like high-pitched tapping noises (not to be confused with the tapping from solid-lifters or low oil-pressure), or unless the Owners' Manual specifically says that Premium is REQUIRED (not just recommended), which is the case in some luxury and high-performance vehicles, the engine will usually run just fine on regular...at a much lower cost. In my area, although there are a few rip-off-stations, 87-octane is currently running between about $2.40 to $2.80, with Plus (91 Octane) between $3.00 and $3.20, and 93-Octane High-Test $3.30 to $3.40. Sometimes you can get a discount through your grocery store with Bonus-points on your grocery card, as with Giant Food and Safeway in my area....and the oil companies themselves offer discounts with their own Bonus and credit cards. But the point is that, in many cases, regular can safely be used, at a big savings in cost.

It used to be that premium gas kept your engine cleaner because more detergent-additives (as per the higher price) went into it. But, today, even regular gas, at least among the Top-Tier brands, has enough additives to keep the fuel system and engine reasonably clean, although some Direct-Injection engines may eventually have problems because of the way they actually spray the fuel into the cylinders, bypassing some places where the deposits can often build up.

To help you find Top Tier stations, here is a general list: Any of these fuels on the list will probably be better for your engine than what you will find at Ma-and-Pa stations, although I particularly like Shell and Chevron, and have generally had my best experience with them. I pretty much use Shell today because Chevron stopped selling in the D.C. area, Shell discounts are available through Giant Food, and Shell has a V-Power detergent package almost as good as the superb Techron package that Chevron uses.

https://toptiergas.com/licensed-brands/

 

My 4Runner says premium for optimal performance.

 

Around here premium is only 20-30 cents per gallon more than regular. I put regular in my Highlander and premium in my GS, both as specified in the manuals.