So the wife filled up the VW with 87 octane

[csandste]

Originally Posted by dbias
Higher octane gas is designed to be harder to ignite and this aspect slightly decreases LSPI.
Most all high octane gas has greatly increased detergents and corrosion inhibitors which helps the fuel system stay cleaner and prolong injectors health. In those vehicles designed to take advantage of it I feel its probably a good thing to use it.


Other than Shell, I can't think of any brand that advertised premium as having more detergents. Of course, I always use a Top Tier gas and do throw in a bottle of PEA every five thousand miles.

 

[MParr]

What is LSPI? A fancy name for engine knock. The Theta II engines are famous for knocking and breaking rods. Higher octane equals less knock.

 

[gathermewool]

Low-speed pre-ignition. Information is all over the Googles

 

[CT8]

So what is the big Deal?

 

[henni]

Famous words by Adam ... "..>"The woman whom YOU gave to be with me.... "<

 

[CharBaby]

Originally Posted by wemay
Originally Posted by Char Baby
I've owned only 1 vehicle that actually allowed for a higher octane and that was a 2001 Lexus RX300. The owner's manual stated(this is not a quote)...87 octane is acceptable and 91 octane or higher is recommended for better performance. It didn't say what performance so, I would assume it was power.

Turns out(from searching) that the power increase was 2 horse power. And in the 15 years that we owned this RX300, I'd fill up with higher octane fuel for several tanks in a row, just to get some form of a baseline.

NEVER ONCE did I ever experience any feel of extra power and my fuel economy at best was the same as on 87 octane. If the fuel economy was ever better with the higher octane, it was so small of a difference that, I may have achieved the same fuel economy on 87 octane for that particular tank of gas anyway(which often happened).

At that time of ownership, if higher octane fuel(91-93 in my area) cost ~10% more than 87 octane, there was no way that I ever achieved 10% extra of anything except 10% more money out of my wallet. Today, this is more like >20% higher..."What's in your wallet?"


That's the crossroads i find myself at as well. Choosing 87 unless any empirical evidence shows o should do otherwise.



Oh, and in addition to this^^^, I have never read a reputible publication in the past 30-35 years that ever said anything different than what the CAR & DRIVER article said.

 

[blufeb95]

Originally Posted by csandste

Other than Shell, I can't think of any brand that advertised premium as having more detergents. Of course, I always use a Top Tier gas and do throw in a bottle of PEA every five thousand miles.

Shell only advertises their premium though, all they say is that their premium has 7 times the amount of detergents than federally mandated, they never say how much detergent is in their regular, it's all top tier gas so I wouldn't be surprised if Shell regular has the same amount of detergent as Shell premium and a comparable amount to most other top tier gas.

 

[Rmay635703]

Originally Posted by LotI
My current 2.0T recommends premium fuel. They also give the blessing of up to 15% ethanol.

In 17k miles I've used 88octane E15 for the majority of the time and smile all the way to the bank. It does return better mileage than 87E10.

p.s. I also ran 15% ethanol in my GTI...and I was sure to let all the snobs on the forums know!


I've had the same summer experience with e15 on my high compression cars.

 

[ARCOgraphite]

I had two cars that assuredly needed high octane fuel.

1 - 1993 Lincoln MK VIII INTECH DOHC V8 with the pre OBDii engine. tune.
'This monster was tuned for POWER and I tried mixing in a 1/2 tank of regular
and on a WOT pull the next day the engine had a HARD knock. NO K sensor working that day.

So much so I thought it was going to break a piston. Whoa! Nellie, back her down!

2- My Dad's 1970 455 Buick hand me down.
I was commuting to school in Lowell , Mass and the gas crisis was on.
Big block and over 10:1 comp
I had to back off the timing and disconnect the secondaries on the Q-Jet.
or it would knock more than Tony Orlando's girlfriend.

The VW does fine on 87. and it's got over 1.2bar turbo boost at 2500rpm.

But It does throw fuel at it. Instant fuel usage on the DIC goes down to 7 - 12 MPG boosting !

And that's just a tiny 1.4 litre ( 85 cubic inch ) motorcycle engine

 

[benjy]

modern ECU's continue to evolve controlling many things better + adjusting for a variety of conditions + fuel, BUT turely different programming for higher octane WILL make a BIG difference. go to the site GOAPR a premier VW + Audi as well as other tuning + see the differences that can be made on a PROPERLY tuned car REQUIRING higher octane can do!! stock measured by APR dyno for the newest E888 2.0T is 221 hp +223 tq VW is sandbagging a bit BUT add APR stage I its 253 hp + 309 tq BUT wait it gets better!! stage II with 93 oct is 261 hp + 317 tq thats using ALL stock from new, theres even more if you change some parts!!! i have + had APR tunes on an 01 jetta 1.8T + now an 01 audi TT 1.8 T both almost 300 TQ but without todays knock preventing DI that allows much more SAFELY!!! manufacturers tune safely for warranty + EPA but some of the the enhanced APR tunes meet EPA testing. ALL turbo'd vehicles harbor more power one way or the other with my 01 jetta a very small twisted downpipe the most important pipe off the turbo was very SMALL + factory boost limited to 7 lb my TT sees 25 lb on my boost gauge when i floor it actinating full power, but only made 150 hp +168 tq. theres a lot of bullpoop these days what an engine can do, but a good ECU tune from APR starts at $600 a simple safe download, + generally the warranty is gone unless you buy the warrantied by APR tune for xtra $$. VW + Audi are the best supported easily modified vehicles made today IMO, not cheap but for the gains surely cost effective!!

 

[SwampSurvivor]

I can't imagine any car not being able to pull timing enough to safely handle it. Power and fuel consumption will suffer i'm sure.

 

[Rmay635703]

Originally Posted by Miller88
I can't imagine any car not being able to pull timing enough to safely handle it. Power and fuel consumption will suffer i'm sure.


Even if it did just gap to a cooler temperature spark plug and 90% of the issue is solved

 

[BAJA_05]

We run 87 octane -- what the gas door recommends in our Jetta in signature with no/zero issues. Techron Complete Fuel System Cleaner every 3000 miles also from day one.

 

[wemay]

Originally Posted by BAJA_05
We run 87 octane -- what the gas door recommends in our Jetta in signature with no/zero issues. Techron Complete Fuel System Cleaner every 3000 miles also from day one.

 

[bbhero]

Originally Posted by wemay
Originally Posted by hallstevenson
VW says to use 87 octane. Why use higher octane ? Self-proclaimed experts that think they know better saying it's not good enough ? Pfffft


The manual says better performance may be had with higher than 87 octane.



Aka your vehicle will run ok with 87...

But going up steep grades pushing the gas hard or flat land driving and really pushing your vehicle hard... Aka your vehicle will not run all that good at all...

But.... You live on flat land USA= Florida...

 

[CharBaby]

I have read/viewed more reviews e.g. on the Mazda 2.5L Turbo where it has ~227hp on 87 octane and up to & > 250hp on higher octane(same torque figs) and there hasn't been a single test driver that has been able to tell the difference when comparing the octane in these vehicles. Maybe there is a very small measurable difference in the 1/4 mile times by a couple of 10s of a second but, that's hardly worth the money.

 

[bachman]

Originally Posted by Char Baby
I have read/viewed more reviews e.g. on the Mazda 2.5L Turbo where it has ~227hp on 87 octane and up to & > 250hp on higher octane(same torque figs) and there hasn't been a single test driver that has been able to tell the difference when comparing the octane in these vehicles. Maybe there is a very small measurable difference in the 1/4 mile times by a couple of 10s of a second but, that's hardly worth the money.


Yeah, that's really where I fit in.
Regular old around town driving and no sporty performance demands so it's the mid grade as default. It's been an impressive vehicle for it's balance. Just the right size for us, better than expected mpg and ride comfort, power and torque that simple delivers what or when is needed.

I likely filled up with premium thinking back to our tour of Ouray, Telluride and Durango because I knew there is plenty of pep or pulling power demands in the elevations, climbing roads and thin air. The CX rode like on a cloud and the mpg was really impressive. I remember it being one of our first real road trips and monitoring economy for the first time. We never recorded anything below 28 mpg.
Our typical city life and daily drives is all stop and go for both cars and I don't even look at mpg except for some hwy.

As someone else mentioned, the APR charts really do illustrate power differences with octane. One would be foolish to not utilize that advantage in competition, spirited driving or even every day if they invested the $1000 or more to get that tune.

 

[ARB1977]

Originally Posted by AC1DD
Originally Posted by ammolab
So VW built the car you wanted, but they aren't able to tell you what gas it uses?

If built and tuned for 87 Octane higher octane fuel does nothing but waste money.


Wrong.

In this case the ECU can take the extra octane and advance the timing and change a few other parameters and get slightly better MPGs and performance.
It's enough to make an extra 20-25 cents a gallon worth it, anything more than that it isn't cost effective.

Even VWs made in the mid 1990s could benefit in this way.

Our 18 CRV with the 1.5LT saw no difference with higher octane. So for me the above statement is correct.

 

[Linctex]

Originally Posted by ARCOgraphite
and disconnect the secondaries on the Q-Jet.


I always cringe when I hear people say stuff like this?

"disconnect the secondaries"??????

Just don't push so hard with your right foot.... sheesh

 

[UG_Passat]

Originally Posted by madRiver
Originally Posted by LotI
It's worth about 5hp, from the Fifth Gear test years ago. It lets VW advertise a wee bit higher number.

It's tuned for 93, but retards timing when used with perfectly usable 87.


The Passat/Tiguan share a detuned for economy 2.0T with Budack cycle engine that produces 184HP but a decent torque number. The GTI you have is tuned for improved HP on premium but can run with slightly reduced power on regular.

The reason the OP notices no difference is that the engine is tuned to run well on regular with a turbo engine because it was design criteria and DI helps. I have the same engine likely in our 2018 Tiguan with 55k and only once did we put in premium as regular not available. Neither wife/nor I noticed any difference in power.


The Passat and Beetle is based on the Tiguan budack but detuned even more to 174 hp and 184 lb-ft. It's more than just detuned, it's different valve timing parameters and a tiny turbo, limiting its potential for tuning