87 octane vs. 91 octane?

Discussion in 'General' started by jhu, Feb 24, 2009.

  1. jhu

    jhu Well-Known Member

    My wife's Passat has the 1.8T engine in it. The manual states that 91 octane should be used, but 87 can be used with slightly decreased performance. I figure that as long as the rpms are in a range that don't give any significant boost, it should be okay to use 87 octane. What are people's thoughts on this?
  2. abcdpeterson

    abcdpeterson Well-Known Member

    Does the manual actualy state
    if the manual says you can use 87, I would try using 87. I would think the knock sensor should adjust the timing for 87.
    if your hyper miling the performance is likly not an issue.
  3. jkp1187

    jkp1187 Well-Known Member

    Knock sensor should adjust the timing. Still, I'd steer clear just because if performance may suffer, fuel economy may suffer, too. (Also, knock retard notwithstanding, I'd be ultra-conservative with a turbo engine - if 91 is recommended, run 91 in it.)
  4. 2008 Civic Hybrid

    2008 Civic Hybrid Serious Hypermiler

    I owned a Passat 1.8T for 6 years before changing to a Hybrid.

    I think the VW Passat 1.8T called for 91 RON. Not 91 Octane.

    See here... http://www.type2.com/bartnik/octane.htm

    Hope this helps.
  5. jkp1187

    jkp1187 Well-Known Member

    The EPA (fueleconomy.gov) says that a Passat with the 1.8T takes premium gasoline.
  6. drimportracing

    drimportracing Pizza driver: 61,000+ deliveries

    I would use 87 for normal driving and 91 for boosted, thrill seeking, law breaking, pee in your pants, hide the kids and animals, I think he is gonna wreck kind of driving.

    I'm a bit of a daredevil though, I get my thrills from opening cereal boxes upside down and getting the prize first, I'm wild like that! - Dale (only thing boosted on my car is the tire pressure.)
  7. drimportracing

    drimportracing Pizza driver: 61,000+ deliveries

    Was that the EPA (evil petroleum assistants) when Bush owned the government or when he was replaced by a man with a soul? (rhetorical) - Dale
  8. hogrod

    hogrod Member

    In my state they have to mark gasoline that contains ethanol, 95% of stations I have used both regular and mid grade are 10% ethanol but premium fuel doesn't have any.

    My car only calls for regular 87oct., but because of the ethanol It has I get much worse mileage running cheap gas. Another nice side effect, the car seems to have much better throttle response with premium.
  9. PILL

    PILL Well-Known Member

    I think it is just in your head. 91 has no more power than 87, it actually resists burning more.
  10. hogrod

    hogrod Member

    I'm pretty sure I said that with higher octane I notice better throttle response, not that it made more power. I assume this is because the computer is adjusting the timing differently when running the higher octane fuel, as most newer cars will do.

    Notice I never specifically said 91 octane? That's because only a few stations around here carry that octane level of premium fuel. Most stations here are 87, 89, & 93 octane for the three levels of fuel.

    Also you missed the most important thing I stated, that only the premium fuel around here doesn't contain ethanol. I loose 5mpg or more just running a 10% blend, so Premium is well worth the extra couple dollars per tank.
  11. Kurz

    Kurz Well-Known Member

    Use 87 but keep an eye on Fuel Economy and Subtle changes.
  12. ALS

    ALS Super Moderator Staff Member

    Ever thought of using 89 octane instead of 87. My manual says to use 91 or higher. Yet 89 octane gets me the same gas mileage as 91-93 in my 740 Turbo. Both cars run fine on 89 and the 960 does get a little better mileage with 91-93. BTW both my cars require premium and they run like absolute garbage with 87 octane. Gas mileage drops like a rock and have a major decrease in HP with 87 in the tank.
  13. jkp1187

    jkp1187 Well-Known Member

    Non-sequitur. Government officials have no souls.

  14. 99LeCouch

    99LeCouch Well-Known Member

    I'd use the 91 or 93. If you ever need to get into boost it won't kill the engine.

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