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Four cylinders at highway speeds

I have two small SUV's- Hyundai Tuscon and Toyota Rav4, purchased in four cylinders for fuel economy. However, on long highway trips, I'm afraid that maintaining a speed of 75 mph might be detrimental to the engines (3000 rpm). I'm FAR from the red, warning zone, but need I drive slower because of the small engines? Also, am I really saving money on the highway with a four cylinder, rather than a six cylinder car with lower highway rpms?
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Comments

  • edited January 2008
    I doubt if you will experience any real problems. It is not the number of cylinders that really is the issue, but rather the possible stress on the engine and I don't think you are there.

    Of course there would be better mileage and less wear if you would slow down to the speed limit.
  • edited January 2008
    I had a Toyota Pick-up with a four cylinder engine and a 4-speed manual shift transmission without overdrive. I was constantly driving highway speeds with RPMs around 3500, and that engine lasted 325,000 miles. The key is keeping up with the scheduled maintenance. The RPMs don't really matter if the oil is changed regularly and the engine kept in tune.
  • edited January 2008
    The engines were DESIGNED to run that way. You're not hurting anything at 3000 RPM.

    I recall a friend who bought a new Volvo in 1974. He asked the same question after a long road trip. I gave him the same answer. He owned that car for 20 years. It had well over 300K miles on it when he traded it for a newer Volvo. For all I know, he may still be driving that one. Granted a Hyundai or Toyota are not Volvos, but the answer is the same.
  • edited January 2008
    You are a victim of tradition, and folklore. Historically, all US cars were 6 or 8 cylinder, and the only 4s were cheap imports that did not last long.

    Then came the VW Beetle, and 4 cyl. Volvos, and the truth emerged that the number of cylinders and engine size did not really matter; it was the quality and design that made these engines last.

    In foreign markets, 8 cylinder cars are rare, and 4 cylinders are the vast majority. I rode in a Toyota Corolla taxi in Asia with had a 4 cyl. diesel with nearly 1,000,000 miles on the original engine. Volvos routinely exceed 500,000 miles on their 4 cyl. engines.

    Domestically we just had a post from a forgetful Neon owner who went 270,000 miles when he broke his timing belt, which should have been replaced much earlier. The car was running great up to that point.

    People who drop dead of heart attacks are seldom the small skinny type. It's the big muscular ones who stopped excercising!! Car behavior is very similar.

    The only exception to this is if you are pulling a trailer; then you need good horsepower and torque top get performance and long life.



    American cars used in urban settings wear out their engines prematurily from starting and stopping, since they don't warm up properly. A smaller engine would actually last longer, since it gets a good workout.

  • edited January 2008
    It's more a matter of adequate power than engine speed. We used to own a 70 hp Honda Civic which was underpowered for our 75 mph interstate speed limit. It's replacement, a four cylinder, 165 hp Subaru cruises comfortably at that speed. Both of your vehicles should do fine at 3,000 rpm. 4,000 rpm would be ok, too, just noisier.
  • edited January 2008
    Most Euroboxes are 4 pot and they survive being thrashed up and down the highways without problem.

    I remember back in the 70's Ford Europe actually built large sedans (Zephyr & Granada) with optional 2.0L 4 cylinder Pinto engines, these were targeted at sales rep fleets to reduce fuel costs - Oil consumption was another matter of course.
  • edited January 2008
    On the contrary it's actually good for your cars to do this. Running at cruise RPM gets the engine nice and hot which will ultimately prolong the life of the engine. Driving on the highway is much less stressful than driving around the city anyway. And these are relatively recent vehicles so you should have no problem. I drive my old Honda (180,000 miles) on the highway at 70-80 mph ALL THE TIME and it keeps on trucking. Just keep the oil changed and you will be a happy camper.
  • edited January 2008
    "I'm FAR from the red, warning zone, but need I drive slower because of the small engines?"

    No.
  • edited January 2008

    If it were detrimental to the engines then my wifes Accords NEVER would have lasted 300k+ miles...and NOT buring ONE DROP OF OIL.
  • edited January 2008
    You usually are saving money. You could drive slower but you don't have to worry about the longevity of the engines.
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