Are Six Cylinder Engines Passé?


Asked by Jul 29, 2016 at 02:12 AM about the 2010 Subaru Outback 2.5i Limited

Question type: General

With all of the advancement of naturally aspirated Fours and greater efficiency
of performance, reliability and fuel economy, do you really need a gas guzzling
six cylinder engine with more repairs and maintenance headache..

16 Answers


I have owned straight six's and V6's and of the two I would stick with the straight 6, maybe it's not the high revving of the V but the low end torque is perfect for everyday low speed pulling, hauling, and if it is in a 4X4 just running around in the sticks, plus the mileage hasn't been too bad, the least one I owned got 18MPG. The V6's on the other hand have been terrible on MPG and torque, what my straight six could hook onto and drive away the V6 struggled to pull out and the best MPG was on 13.8. So V6 gets a fail and the straight 6 a passing grade. But overall the engines, give me a small block V8 for the everyday stuff.

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tennisshoes,. Thanks...hey, what do think about the relative torque of the "boxer engines" , they're in a separate class from V6s.. The 180 degree angle of opposed cylinders gives them a natural balance ? The 3.6 H6 up until the 2015 with the CVT was a real gas hog.. While not a barn burner, the little 2.5 H4 can actually tow 2,700 pounds, quite a lot for its size, wouldn't you agree? And, the H4 gets pretty decent mileage with the CVT,. 22 city and 29 highway.

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They scare me, it looks like they took the basic design from Chevrolet Corvair and did modding to make it water cooled, back in the day the Corvair performed rather well and got decent mileage right up till they started blowing head gaskets and developed crankshaft problems.


tennisshoes-. I understand your concerns, they have had plenty of problems with head gaskets in the past, no question. The new ones are much better. I wouldn't consider comparing them to an old Corvair or VW Beetle air cooled engine.. You know, they use "boxer engines" in some aircraft applications?? If they were that "unreliable" ,. I don't think they would do that? So, what do you think about the torque question? It pulls pretty well for a small Four, and tows my trailer pretty well.

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Looks good for that small of an engine, but I would not be towing anything with that transmission without some modifications to its cooling.


Actually, the CVT works very well for towing. Of course, my teardrop trailer is only 1,000 pounds, fiberglass composite. The CVT transmission has it's own built in cooler. Subaru and other experts told me to skip adding another layer; would only add another point of failure to system.

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The car is rated to tow 2,700 pounds for the H4 and ironically , the larger H6 with more horsepower is only rated to tow 3,000 pounds. not much of a difference here .

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That is a chance you take when you add anything on a vehicle, at least put on a trans temp gauge.


tennisshoes- has a warning light built into the ECU on dashboard, plus, they state in the owner's manual to not tow higher than 105 degrees and 1,300 pounds. Fortunately, I'm only at 1,000 pounds. Adding extra gauges to the very complex electronic control unit in this car is not an easy thing to do, Subaru advised not doing it. Yes, I'm very careful towing and appreciate your comment and concern.

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Tennisshoes has been right on, and is referring to a TRANSMISSION fluid temp gauge, not the engine coolant light you were persevorating about on another thread. Adding an actual CVT fluid temp sensor mounted through a drain or fill plug adaptor is very easy. I use such a setup with an added ATF cooler on my SC'd Miata, as the trans temp is the limiting factor in this scheme of things. The same holds true for the Subaru, in that the towing limit is set by trans fluid temp rather than motor oil temp or the smaller size of the 2.5i relative the the 6. (Indeed, commercial trucks outside of North America struggle to pull HUGE loads with frugal small motors, using ultra-low gearing as necessary on hills.)


Re: "six cylinder...headache." The correlation between cylinder number and failure rate or maintenance cost is relatively weak, Mark, as DESIGN trumps number count. Manufacturers have migrated toward 2 Liter 4 cyl blocks with direct injected heads as the most efficient designs, pressurizing when necessary for compactness and efficiency that betters 6 cyl designs, at the risk of higher temperature management issues. If purchasing a USED vehicle, I'm more apt to trust a larger NA motor than a smaller pressurized one, for example. With the Subaru that even holds true at the 4 cyl option, wherein the 2.5i NA has been normally safer for users' pocketbook than the 2.0T in the long run. Yet turbos are becoming ubiquitous, despite moderate cost, as the only way to get high output and reasonable fuel eco. Seems that VW/Audi, and now BMW and Ford, are getting prodigious performance from their blown 2.0T's, for example.


I agree completely with you that it's better to have the naturally aspirated engine with larger displacement over a puny powerplant with a turbo or supercharger... Seems to me that they are frequently abused and called upon to deliver power in the most stressful situations. And, when the turbo goes, it's going to cost a lot. If you want to experience a turbo, go rent one... they're fun, but, it doesn't mean I want to live with one! I recently went to a car show and saw an old vintage Mercedes Benz with a 2.5 liter V8, now that is some small cylinders...,if you ask me, I'd rather have the 2.5 Four. The only point I was making about the H6 3.6 engine is that it's very wide in the engine bay, weighs almost 200 pounds more, and has less clearance for your tools or your mechanics tools... Plus, it certainly burns more fuel....All this for towing an extra 300 pounds, that's it? Yes, it may be a little quieter, and get to 60 in a couple of seconds, probably 1.5 or so, but again this was ONLY important in high school. Finally, my teardrop trailer weighs 1,000 pounds maximum and it's not even more than 36 percent of the total tow, I'm really not worried about overheating. Besides, I'm really careful and don't push it when towing..... here's a picture of my rig..

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Ernie, where exactly would you suggest installing a temperature gauge for the transmission without having some UGLY device hanging out from under the dashboard???

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By the way, it's interesting that the difference in towing capacity is 300 pounds and that the weight difference between the H4 and H6 cars is 272 pounds for the larger engine.....

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That's almost 300 pounds more right up front to manage when making turns.....I'd rather have the more agile steering over the gas guzzling H6...

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A pod kit, they go right on the windshield pillar. look good too. You can even paint them too match your interior.

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