I have a 2016 VW Passat 1.8t. Runs fine on 87 in the Central Texas heat. 140k at the moment and running great. Just sharing my experience. Tried 91 and got worse MPG and no noticeable feel in performance or any noises. Go figure.
Using regular 87 octane on a turbo engine
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I can't imagine how this would be applicable with a turbo and warming strategies.
Ok but recommending a GM product as an alternative? I'd rank them just as unreliable and I get to enjoy a lower quality vehicle instead.
And yes the Audi will suffer the exact same fate, then it will be sold and on to the next car. It's simply not economical to maintain cars here due to rust and suspension wear. To replace all suspension bushings and to properly do all 4 shock/struts (IE spring isolators, bump stops, strut mounts, OEM strut/shocks) you're looking at $10k of parts and labor.
that is what I'm trying to fish for in this thread because somewhere there is an engineer or engine tuner that is familiar with an ignition timing table like this:
notice the slope when things are hot, the ECU pulls more timing to prevent knock. but on the other side, there exists a large region of air intake/engine temps where knock is not expected and the engineers have programmed the base timing.
Theoretically this graph would continue much further to the region I'm talking about, down to intake temp -40, -50, -60 etc but there would be no timing changes simply because these are not expected running conditions. That's my argument, when its 0F out there is so little chance of pre-knock or knock that 87 or lower is fine, it's just not ever tested.
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| Temperature (°F) | Temperature (°C) | Estimated K | Effective OI | Relative Knock Resistance Gain (%) | Equivalent AKI Rating |
|---|---|---|---|---|---|
| 104 | 40 | -0.51 | 97.1 | -0.9 | 87 |
| 86 | 30 | -0.69 | 98.9 | 0.9 | 88 |
| 68 | 20 | -0.88 | 100.8 | 2.8 | 89 |
| 50 | 10 | -1.06 | 102.6 | 4.7 | 90 |
| 32 | 0 | -1.24 | 104.4 | 6.5 | 91 |
| 14 | -10 | -1.42 | 106.2 | 8.4 | 92 |
| -4 | -20 | -1.61 | 108.1 | 10.3 | 93 |
| -22 | -30 | -1.79 | 109.9 | 12.2 | 94 |
| -40 | -40 | -1.98 | 111.8 | 14.0 | 95 |
Here is what Chat GPT spit out when I asked it to analyze studies of temperature vs equivalent octane rating. Its basically saying that at freezing, your 87 octane has the same anti-knock as 91. Any petroleum engineers out there?
Gonna be a bit difficult to get any useful operational info, much less real world results on a turbocharged engine with intake air temps at -40 or lower. This may be a "duh" statement, but turbos compress air, which in turn heats it up. So, even with an intercooler, which has it's own heat retention ability, you're probably not going to routinely get IAT at or below zero, much less -40.
Thinking you're going to be able to "get by" with 87 due to lower intake temps in really cold weather may or may not work out well. Thats a maybe I personally wouldn't risk on an expensive vehicle like an Audi. BUT, if you expect it to be clapped out, and needing a serious influx of cash to maintain it after a short amount of time, and expect to get rid of it, well, send it. Let us know how it works out. Just remind me never to buy a used Audi from north of the border
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Thinking you're going to be able to "get by" with 87 due to lower intake temps in really cold weather may or may not work out well. Thats a maybe I personally wouldn't risk on an expensive vehicle like an Audi. BUT, if you expect it to be clapped out, and needing a serious influx of cash to maintain it after a short amount of time, and expect to get rid of it, well, send it. Let us know how it works out. Just remind me never to buy a used Audi from north of the border
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Once the engine, along with all of the fluids are up to operating temperature, I can't see how ambient air temperature would have much, if anything to do with what octane level the fuel is. Especially under demanding conditions.
Datalog showing difference 87 to 93 in our Atlas with a NA VR6 rated for min 87. Turbo or not unless you log it you really have no idea what is actually going on. This is 2025 not 1984. ECUs are v. sophisticated and preemptively manage timing to deal with detonation...if you're even getting any. If Audi says you can run it you can run it safely. Post in thread 'Switching to Premium gasoline' https://bobistheoilguy.com/forums/threads/switching-to-premium-gasoline.385860/post-7167252
I think this topic involves calculated wear risk much like the start/stop debate and thick vs thin debate.
If the ECU is pulling timing and potentially richening the air/fuel ratio through specific rpm ranges (or ranges of direct injection where pre-ignition is most likely to occur), this is all well and good in keeping acute damage at bay. However, this may come at a price. Late spark timing (meaning spark event later than ideal for the mixture, pressure, and rpm) means lower combustion efficiency causing a slower rate of thermal decay, higher exhaust gas temperature, greater propensity for soot and piston/chamber/valve deposits, and reduced volumetric efficiency. Richer AFR means more fuel mixing with the oil on the cylinder walls and around the rings, and thus more fuel dilution in the sump. Higher EGTs could increase turbo wear as well.
Though the engine may be able to run on 87 through smart technology, that doesn't mean it's running optimally. Wear rates could be higher due to these suboptimal conditions. Such an increase could be "acceptable" per the OEM. Keep in mind this is the same OEM that says a quart of oil consumption every 1,500 miles is "normal." Their standards for "normal" are sometimes a bit nuts.
Intake air temperature will be lower, though not as cool as ambient due to heating of the air along the intake tract, but air density is also higher thus the fuel demand is higher for a given volume. That skews that data some which I don't think Google AI is accounting for. That scenario is far too complex and dynamically variable for the AI to just pull random numbers and spit out an accurate graph. Having seen datalogs of various racing engines, no two reacted the same to changes in ambient air temp and fuel temp. That higher density mixture needs less spark advance for peak efficiency anyway.
If the ECU is pulling timing and potentially richening the air/fuel ratio through specific rpm ranges (or ranges of direct injection where pre-ignition is most likely to occur), this is all well and good in keeping acute damage at bay. However, this may come at a price. Late spark timing (meaning spark event later than ideal for the mixture, pressure, and rpm) means lower combustion efficiency causing a slower rate of thermal decay, higher exhaust gas temperature, greater propensity for soot and piston/chamber/valve deposits, and reduced volumetric efficiency. Richer AFR means more fuel mixing with the oil on the cylinder walls and around the rings, and thus more fuel dilution in the sump. Higher EGTs could increase turbo wear as well.
Though the engine may be able to run on 87 through smart technology, that doesn't mean it's running optimally. Wear rates could be higher due to these suboptimal conditions. Such an increase could be "acceptable" per the OEM. Keep in mind this is the same OEM that says a quart of oil consumption every 1,500 miles is "normal." Their standards for "normal" are sometimes a bit nuts.
Intake air temperature will be lower, though not as cool as ambient due to heating of the air along the intake tract, but air density is also higher thus the fuel demand is higher for a given volume. That skews that data some which I don't think Google AI is accounting for. That scenario is far too complex and dynamically variable for the AI to just pull random numbers and spit out an accurate graph. Having seen datalogs of various racing engines, no two reacted the same to changes in ambient air temp and fuel temp. That higher density mixture needs less spark advance for peak efficiency anyway.
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My 2024 GTI has the EA888 evo 4 engine and is recommended to run 87. I’ve seen several YouTube videos of tuners running dyno tests the show no increase in power btwn 87 and 93. Only gas it’s ever had is Sunoco 87 and I honestly don’t drive it very hard so I think I’m pretty safe doing this.
If the manual calls for min 87 octane, that should mean up until that low it can prevent/minimize knocking through timing adjustments. Sure your torque curve will be pushed down a little bit, which you can easily more than compensate with moving to a lower gear.
As long as you don't move below what the manual says as the min acceptable grade, i would expect you to be just fine.
I could only read a couple of the comments here. Gosh they are so hateful! I would not consider Audi a driver's machine, especially an SUV. My understanding is that you are looking to buy a relatively safe and luxury/comfy car that has a good logo on the grill to drive around. That car with a bit lower horsepower will do just fine. Who would want to waste money anyways?
Well, if you were asking this question for a Ferrari Testarossa, or a Porsche Turbo S, i would probably also say that using the lowest grade possible grade is not a good idea. If you said "hey I can afford vehicle if and only if i fill it with regular gas" again, perhaps Audi is the wrong choice (in the sense that you need some headroom in case somethings breaks anyways). But in your case this is a very sensible question, with a very logical thinking you already have done in my opinion
As long as you don't move below what the manual says as the min acceptable grade, i would expect you to be just fine.
I could only read a couple of the comments here. Gosh they are so hateful! I would not consider Audi a driver's machine, especially an SUV. My understanding is that you are looking to buy a relatively safe and luxury/comfy car that has a good logo on the grill to drive around. That car with a bit lower horsepower will do just fine. Who would want to waste money anyways?
Well, if you were asking this question for a Ferrari Testarossa, or a Porsche Turbo S, i would probably also say that using the lowest grade possible grade is not a good idea. If you said "hey I can afford vehicle if and only if i fill it with regular gas" again, perhaps Audi is the wrong choice (in the sense that you need some headroom in case somethings breaks anyways). But in your case this is a very sensible question, with a very logical thinking you already have done in my opinion
Wow. This is so annoying. Clearly the manual doesn't say it's "ok" to run 87.
I run top tier 87 in my TT Tundra. It calls for it. I’ve tired 89 and 93 with no change in performance or gas mileage.
I have an A6 with a 3.2. Completely different engine but the fuel door says premium. I’m cheap and put in 87 and have pinging in the summer so I have been mixing premium and regular to make mid grade and the pinging immediately stopped. I never had pinging with colder temperatures so I will go back to regular in the fall. So if it pings, mix in some premium.
PS I drive an old Audi because it was cheaper than a Japanese car.
PS I drive an old Audi because it was cheaper than a Japanese car.
Cough, cough… E85?
I’ve done this in the past as well with the q5 (q3 also) and used only 87. I drove them both like it was gonna be somebody else’s problem, and neither vehicle missed a beat.
Last car (Fusion) was DI turbo and current car (Malibu) is DI turbo and both recommend 87. Not once have I used anything higher. Both did/do fine.
Don’t always use top tier fuel either. Most of the time I will. But not always. Sometimes a clean bathroom and/or decent snacks is the most important thing so I’m stopping at Buc ee’s. And I ain’t making two stops.
Don’t always use top tier fuel either. Most of the time I will. But not always. Sometimes a clean bathroom and/or decent snacks is the most important thing so I’m stopping at Buc ee’s. And I ain’t making two stops.
OP, I'm sure that the engine will last to it's warranty period on 87, I don't think many people would buy these vehicles if the manual stated DO NOT USE 87 octane fuel.
That being said, I don't know how well these engines do on 87, maybe the low octane map is good enough there will be no amounts of detonation but only a large reduction in power.
For the long haul, going way beyond the warranty period, I would suspect the 91 or higher will be easier on the rod bearings. It's not the detonation you can hear, it's what's going on that you can't hear in which the sensors are picking up before you notice it.
This doesn't apply to just Audi's, but many high compression engines, forced or NA, and especially port injected. DI engines are easier on bearings reducing the risk of detonation. LSPI can be problematic but a different topic.
That being said, I don't know how well these engines do on 87, maybe the low octane map is good enough there will be no amounts of detonation but only a large reduction in power.
For the long haul, going way beyond the warranty period, I would suspect the 91 or higher will be easier on the rod bearings. It's not the detonation you can hear, it's what's going on that you can't hear in which the sensors are picking up before you notice it.
This doesn't apply to just Audi's, but many high compression engines, forced or NA, and especially port injected. DI engines are easier on bearings reducing the risk of detonation. LSPI can be problematic but a different topic.
