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Best Fuel Octane

Matias

Passed Driver's Ed
Location
Uruguay
Hello,i have a 2015 gti dsg,where I live I get 2 types of gas, normal with 95octane and premium with 97octane,which one should I be using?Should I also add up an octane increasing additive?

Take into account that octane measurement here is not the same as us, on gas stations it is stated as "95 OCTANE" and "97 OCTANE"
I think the octane measurement in my country is RON.
 

Finglonga

Drag Racing Champion
RON means, Research Octane Number and it will tell you on the fuel filler flap what you need for your car.;)
 

toledospeed

Go Kart Champion
Location
3rd rock
Hi Matias, for best performance you should use your premium 97. I would also check for ethanol content to see what the percentage is there. I know some South American countries are big on ethanol, but I don't know if that has changed over the years (Brazil etc.). Many of us in the USA with tuned cars run E20 to E30 (20 to 30% ethanol) because the ethanol keeps cylinder temps down and timing retard at bay. Most gas here in the USA is already 10% ethanol by government mandate.
 

Matias

Passed Driver's Ed
Location
Uruguay
Hi Matias, for best performance you should use your premium 97. I would also check for ethanol content to see what the percentage is there. I know some South American countries are big on ethanol, but I don't know if that has changed over the years (Brazil etc.). Many of us in the USA with tuned cars run E20 to E30 (20 to 30% ethanol) because the ethanol keeps cylinder temps down and timing retard at bay. Most gas here in the USA is already 10% ethanol by government mandate.

Hi!Is ethanol a bad thing?Yes I think nothing has changed here.
 

toledospeed

Go Kart Champion
Location
3rd rock
Hi!Is ethanol a bad thing?Yes I think nothing has changed here.

Just read and it has 10%ethanol

It is a great thing if you are looking for performance. It is bad if you are looking for the best fuel economy. Ethanol is considered "God's Nectar" by many here, LOL. Like I mentioned, many owners with tuned cars go with mixes higher than the typical 10% since it keeps cylinder temps cooler, prevents detonation, and thus allows ignition timing to advance nicely without the ECU "pulling" it under WOT when it detects instability.

See the dedicated ethanol thread here:
http://www.golfmk7.com/forums/showthread.php?t=14213

Calculators for mixing:
http://www.wallaceracing.com/ethanol-mix-calc.php
http://www.georgebelton.com/E85Calculator.php
(Note: there are also apps for smartphones that are even more sophisticated to help keep your blend % static)

That said, I'll give you my "current" opinion on the subject. I like to start by showing that VW/Audi approved up to 15% ethanol in 2015 cars and newer. This should squelch the fears of anyone that fears moving a bit beyond the normal 10% pump gas:
http://www.ethanolrfa.org/2014/11/automakers-approve-e15-for-use-in-two-thirds-of-new-vehicles/

My car loves the "God's Nectar". I upgraded my 1.8 Golf's turbo to an IS20 and run higher boost. I find it necessary, beyond a certain boost profile in given weather conditions, to not regularly see timing pull in my logs. What it does for the car is simply amazing. That said, I am a bit skeptical of regular usage of blends that have a lot higher than the 15% ethanol content for the long term. At the current time, until we see more cars running E30 for years without issues, I am only comfortable using 20-25% (E20-E25) on a somewhat regular basis. That is ~2 gallons of E85 added to per fill up mixed with 93 octane (for a near empty tank). The E20-25 is all I find that is necessary for what I am doing with my car. Going beyond that doesn't make sense for me. Every 5 tanks or so, I plan to put in only regular 93 octane so I can reset my mixture. Typically before a long trip is a good idea since I want to see the best fuel economy anyhow. Also, in the Winter when roads are horrible, I'll stick with regular fuel to limit my year around usage of higher percentages of ethanol. I would also never use it if I planned to store my car or if I didn't drive very often (more on that below).

Historically, ethanol was given a bad rap by some. This is due to several factors, even political factors, but I won't go into that side of things. Many older cars and their owners had issues with ethanol since their fuel systems were not designed for it (fuel injectors, pumps, seals etc.). I was one of them :( Ethanol blended fuel can be corrosive as it absorbs water from the air. The moisture factor can be a big problem for cars, boats and lawn equipment (especially older models) that are not used regularly. For example, I was running 10% ethanol in my 1990 300zx (94 octane from Sunoco for those that remember), but the injectors were not up to the task. After a few injector failures, I sent my failed injectors to a guy doing analysis on the problem. He sent me some amazing pics showing how my OEM injectors had failed due to the ethanol eventually penetrating the seal over time and destroying the internal circuitry. That left a sour taste in my mouth for years. But, newer cars and equipment can tolerate higher amounts of ethanol and now fuel producers also add corrosion inhibitors by mandate.
 
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