Oil & Gas, whats the real truth

I have heard about twenty thousand different things pertaining to which gas to use, which oil to use, and how often to change my oil. I was hoping maybe to find a true answer.

For instance I heard that if you buy your gas at a second tier gas station rather than Exxon, Chevron, etc it has more water in it, that there is something called first hand gas and second hand gas? Also comsumer reports said there is no difference if you change your oil every 3k or 5k miles? Does running 93 octance vs 89 or 87 really give my car any advantage or does it just slowly eat away at my wallet? And last but not least my Honda recommends 5w-x(x cuz I don't know the number off the top of my head) oil and I tend to just put 20w-x oil, is this bad?

Thanks in advance.

For instance I heard that if you buy your gas at a second tier gas station rather than Exxon, Chevron, etc it has more water in it, that there is something called first hand gas and second hand gas?

Never heard of that - sounds a bit fishy, but not impossible. I wouldn't be entirely surprised to find that no-name gas stations have poorly maintained tanks, etc., and thus serve poorer-quality fuel.


Also comsumer reports said there is no difference if you change your oil every 3k or 5k miles?

In most cases, they're probably right. It does vary from vehicle to vehicle, though, and it varies based on how/where you drive. The type of oil you use also can make a difference. My current vehicle does just fine with 10k-mile intervals, running 5W-30 synthetic. ('03 Mini Cooper)

Does running 93 octance vs 89 or 87 really give my car any advantage or does it just slowly eat away at my wallet?

Depends on the car. In all cases, using higher octane than recommended is a waste of money. In some cases, you can get away with using lower octane fuel with little or no penalty. Cars with active knock suppression can usually get away with using the cheap stuff, even if higher octane is spec'd, with only a slight performance/economy penalty. Don't try running lower octane fuel in a car w/o active knock suppression, because you may have knock problems...

And last but not least my Honda recommends 5w-x(x cuz I don't know the number off the top of my head) oil and I tend to just put 20w-x oil, is this bad?

It's definitely bad for your wallet, since you're probably using about 4% more fuel than you need to, just to push that "thick" oil around in your engine. Tough to say whether it's bad for your engine or not (my guess depends on climate, hot=no, cold=yes), and it's tough to say what effect that would have on your emissions equipment. Use the right stuff (5W-30) and quit worrying about it.

good advice, thanks : )

octane is only going to be an extention of timing and compression. higher octane means the fuel will ignite slower, but will also handle more compression and higher temps before combustion. So if you are already running low compression and haven't advanced the timing then anything above 87 octane is only going to hurt performance because it will actually retard timing a bit. But if you bump up the compression or advance the timing you will need the extra octane to prevent detonation

Cars with active knock suppression can usually get away with using the cheap stuff, even if higher octane is spec'd, with only a slight performance/economy penalty.


You should never rely on a knock suppresion system to work all the time.
Engine knock can occur accross such a wide range of frequencies at differnt RPMs that its not always possible to for the sensor to detect it.
Iv heard thier generaly only about 90% efficiant at detection from a technical department head at Honda.

Subaru got bitten badly by this in Australia, the first generation of WRX Imprezzas there were issued with a recal after a large number of them suffered engine failures after being run on to lower octane fuel, and the knock sensor not being able to detect all the knock conditions. Subsequent models sold there then had lower boost levels and differnt ECU tuning to the rest of the world untill the current model was released.

there is no difference between a cheap gas company and a major one. In fact if you pay attention, you will see a exxon or 76 truck pull up to the cheap station and fill their tanks.
the only reason a gas station would have water in their fuel is when the fuel is fresh from the truck.
so I always avoid going to a station when the truck is there or just left.

I personally can feel a difference when I run 87 octane in my 94 Saturn SC2 than I can when I run 92 Octane. I prefer to use 92 octane. The 92 helps my performance.

I would use the 5w-30 oil through your car. Unless you live in a very cold climate weather 20w is way to think of oil to be running through your car. I have been using 5w-30 oil in my car and the weather around my area can get down to -10 degrees and my car still runs great.

Personally I prefer Quiktrip and Phillips 66 over any other gas station but I also heard from many people especially my father that most gas stations are the same. And I work at the airport and I sell fuel and check the fuel that goes down our ground tanks. And just like the gas stations if I don't do a good precheck on the fuel than some water will transfer into the fuel. So any gas station might have water in it, you really can't tell.

No matter what my father tells me I like to change my oil at 3k b/c I like to make sure my car is running healthy. B/c if your oil goes bad your car might not break down right away but over time the used oil can cause your cylinders or crankshaft to wear down. Since I change my oil all the time, my car runs great even though I drag it sometimes.

The difference in fuel quality between stations mainly depends in how good condition the tanks are in.

But there have also been other differences, to cut costs the gas companies have sometimes accepted a higher sulfur content and this have caused large problems for cars with Nikasil-liners.

Modern cars use active knock regulation systems, this means that they work on the limit to knock and a slight degree of knocking is normal. Saab has replaced the normal knock sensor with a system that can sense knocking (and many other things) by measure ionisation current over the spark plugs. Basicly the system senses the pressure and temperature in the cylinder much like the pressure sensors which is commonly used when developing engines; so it won't have the standard problem of separating mechanical engine noise from knock. Saab have had this in production for almost 15 years but I don't know any other manufacturer that uses it (except the Opels with Saab engines).

there is no reason not to change your oil as often as reasonably possible.
Oil is cheap, engines are not.
I use Royal Purple, and at $7 a quart, I still change my oil every 2k miles because you'r better safe than sorry. even if the oil or engine says it will last for 5 or even 10k between changes, why chance it?

i agree to change your oil all the time. I use the synthetic oil and even though it says it lasts over 3k I still change my oil between 2k and 3k.

Posted by viper8369 - 12-16-2003 at 10:09 PM

"I would use the 5w-30 oil through your car. Unless you live in a very cold climate weather 20w is way to think of oil to be running through your car. I have been using 5w-30 oil in my car and the weather around my area can get down to -10 degrees and my car still runs great."

Not to be nit-picky, but since this is the "technical" section, I will correct that statement. The colder the climate, the lower weight or thinner oil you use. 20w oil will take considerably longer to warm up and for its viscousity to reach a level sufficient to do its job. 10w30 is usually the maximum weight oil most new cars will take, and 5w30 is generally the recommendation. Also note, that due to tighter clearances in engines now adays, running a heavier oil could increase oil pressure enough to do damage. There are even 0w20 and 0w30 weight oils (synthetics) that some european cars use (mercedes comes to mind) but also 0wX0 weight oils are recommended to individuals who operate their cars in extremely cold weather climates. Unless you regularly experience sub-zero temperatures, 5w30 weight on newer cars is usually the way to go. As always though, check your owner's manual for your engine's specific requirements.

Thank you fellas. The advice and recommendations are much appreciated.

there is no reason not to change your oil as often as reasonably possible.
Oil is cheap, engines are not.
I use Royal Purple, and at $7 a quart, I still change my oil every 2k miles because you'r better safe than sorry. even if the oil or engine says it will last for 5 or even 10k between changes, why chance it?

Why wait even 2000 miles then? I'm sure you could afford to do it daily if you wanted to. Better safe than sorry, right?