What octane to use?

mdewalle · Post by **mdewalle** » 29 Mar 2016, 11:55

From time to time I put high octane (i.e. 93) in my 2001 V70 2.4T. The rest of the time I use 89. I tell myself the car runs better, is faster and even the weather improves when I use 93. But I know the manual says regular unleaded is fine.

Can somebody comment if I'm just wasting my money paying for high octane gas?

- marc
2001 V70 2.4T

zanzabar · Post by **zanzabar** » 29 Mar 2016, 12:49

You most likely can't notice the difference. If you run it hard at high rpm... possibly, but still the engine computer will change the timing parameters, etc, to ensure that the engine runs smoothly. With that said, high octane will make it easier for the engine to manage all those settings within the established parameters. High compression, high rpm, and turbo engines will generally run better with high octane because the octane level determines how like a pre-ignition event ( = "knock") will happen. High octane makes knock more unlikely.

I believe the compression ratio on your engine is only 8.5 or 9.0, so 93 octane is not really necessary. Some of the later Volvo 2.0 turbos are up around 10.0. My wife's 2014 Ford Focus is 12.0. I would suggest that >91 octane only necessary for compression ratios > 10:1. 89 is fine for 9-10, and 87 is fine for < 9:1 compression ratios.

More info here: http://www.carbibles.com/fuel_engine_bible_pg3.html

Tonyx · Post by **Tonyx** » 01 Apr 2016, 08:49

Anecdotal reply here: I've been using 87 octane for 5 years without any issue. I do notice I get 2-3mpg better with 92 octane fuel a few time I tried it. So about 8% better mpg for 20% higher fuel cost(at least in my area).

Post by **regent** » 01 Apr 2016, 09:13

In theory, the Engine Management will still handle lower octane fuels with the trade-off of degraded performance due to retarded ignition timing. I run mid-grade top tier in my 02 S60 n/a and can't say I have noticed a significant difference but I still know the engine is quite happier with it than if it were to drink 87.
There is also some difference in efficiency between summer/winter due to winter time fuel additives

mdewalle · Post by **mdewalle** » 03 Apr 2016, 14:23

Good info guys; I appreciate it. I might just go to mid-grade and do that habitually.

- marc

mdewalle · Post by **mdewalle** » 03 Apr 2016, 14:26

@regent I noticed your 340 DL in your signature. Isn't that the Volvo line that was built in the former DAF factory in the Netherlands? I grew up there and recall when DAF was in financial trouble they made a deal with Volvo to build smaller Volvo's for then and some of the DAF's were sold under the Volvo brand.

- marc

Post by **oragex** » 03 Apr 2016, 15:54

Tonyx wrote:Anecdotal reply here: I've been using 87 octane for 5 years without any issue. I do notice I get 2-3mpg better with 92 octane fuel a few time I tried it. So about 8% better mpg for 20% higher fuel cost(at least in my area).

Same here. As long as the engine doesn't 'ping', it's a matter of cost. I would not go with 89 octane. Little known, but many gas stations (including largely known brands such as Shell) are not exactly honest with the octane grade they sell. The low 87 octane should be fine, but the 92 octane is not always true because some truck drivers have fun pouring some 87 octane gas in the 92 reservoir.

Post by **regent** » 04 Apr 2016, 11:45

mdewalle wrote:@regent I noticed your 340 DL in your signature. Isn't that the Volvo line that was built in the former DAF factory in the Netherlands? I grew up there and recall when DAF was in financial trouble they made a deal with Volvo to build smaller Volvo's for then and some of the DAF's were sold under the Volvo brand.

- marc

Marc,
DAF's financial trouble or not - that I don't recall. What I remember is that my diesel Volvo was fun to drive and fun to work on... long time ago. Yes, it was made in the NL with the 4-cyl Renault engine, and I got it almost for free from the previous owner who had warped the head and thought it was ...beyond actionable repair (poor compression and an oil leak that had killed the clutch). I shaved the head, put in a new gasket, new RMS and T-belt, rebuilt the clutch, and in three days I was the proud owner of a like-new car with less than 80,000 km on the clock.

Checksix · Post by **Checksix** » 09 Apr 2016, 19:27

What octane is needed depends a lot on how the car is driven. Drive with a heavy foot or a trailer, then I'd recommend the higher octane. Drive like there is an egg between your foot and the pedal and not much load (trailer or mountains) and 87 octane works best.

I've been driving 87 exclusively EXCEPT when pulling my small camper and to tell the truth I get better gas mileage with it than 92.

As an added note about brands of gasoline. I've also run Chevron exclusive except when on a trip and I can't get it. I did an ETM replacement the other day, and after pulling the manifold off I could see the intake vales. They looked new with no hint of any build up at all (175K miles). I drive with a light foot and that helps as well, but I think the Chevron gas used is the reason.

Checksix

Paul_okie · Post by **Paul_okie** » 08 Aug 2016, 14:32

I know this thread is a few months old, but it's been 100 degrees plus for several weeks here. My 2001 V70 2.4t was running horribly. I put some 100% gasoline 91 octane in a nearly empty tank and it ran like a different car after a few miles. It had even stalled on me earlier in the day after backing out of my driveway. So, there could be a hundred different factors involved, but I think the 10% ethanol that's in all the gas around here is partly to blame, and high air temps just make it worse. I really hate to pay for premium or even 100% gasoline (vs. 10% ethanol) - so, I'll probably try to switch back to normal 87 octane when the air temps come down and see what happens. I've also considered just using Lucas Oil in every tank of regular 87 octane.