Hey guys, this is some msg that i asked 'bout tune-up/oil change from beav in private msg. thought that some of you might be interested to know so i move it over here.
feel free to ask/post, guess beav will reply it very good.
happy thanksgiving!
quote:
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SSSVX wrote on 11-16-2001 01:49 AM:
Beav said:
"Tune-ups no longer exist. Most '100,000 mile tune-up cars should have plugs somewhere around 40-50,000 miles"
In the days of Ford Model Ts a complete tune-up included a carb rebuild, engine bearings, etc. Later cars included points, condensors, cap & rotor, adjust carb and timing, etc. Modern cars have spark plugs, some still have spark plug wires and that's about it. No adjustments possible/available. The computer constantly adjusts (or "tunes") the sytem. Double platinum spark plugs can last to 100,000 miles (in a car with computer-controlled ignition and fuel injection) but that just means the plugs will definitely be garbage by then. Long before 100,000 miles the spark plug electrodes will have eroded and caused their gap to widen. This causes the coil(s) to consume more energy in order to fire across the wider gap. This induces extra strain on other ignition parts such as the amplifier (ignition module) that feeds current to the coil(s), the coil(s) itself and the plug wires. If a cylinder begins mis-firing the result could be unburnt fuel in the cylinder washing the oil from the piston and cylinder wall, causing premature wear of those parts and the piston rings. When the rings start wearing then crankcase pressures rise and start sending excess oil mist into the intake system and coating the injector tips with gunk. Now a set of plugs doesn't quite cure anything. Of course this is taking things to their logical extremes, but that happens more often than you'd think...
Remember, extra strain causes parts to go bad earlier. Which would you rather buy, two sets of plugs or an ignition module (anywhere from $250 to $900 + diagnosis and labor) and one set of plugs? The reason the OEMs state extended service intervals is purely from a marketing perspective. It makes it seem like you're getting some real value when you spend $25,000 for a PT Cruiser. What do they care? You're long out of warranty by then.
"Same goes for oil change intervals beyond 3000 miles. Even with synthetics contamination occurs."
Piston rings don't completely separate the crankcase from the combustion process. Some of the combustion gases, which carry particulate matter and corrosive gases, will slip past the rings and into the engine oil, contaminating it. Also engine oil is a petroleum product and as such it is hygroscopic, in other words it attracts and holds moisture. In an engine this moisture comes from the atmosphere and hopefully not leaking gaskets, etc. Combine these two processes with additive package depletion and viscosity breakdown (a term of simplification) of non-synthetic mineral oils (this is where synthetics really shine.) Add in short driving cycles - trips less than 30 minutes of cruising speed where the oil isn't held at a higher temperature for enough time to allow evaporation of non-particulate contaminations - and you end up with poor lubrication. Poor lubrication yields premature engine wear, yadda, yadda, yadda... Let's do the math: 150,000 miles / 3,000 mile intervals = 50 oil changes x approx. $20/oil change = $1000. 150,000 / 7500 = 20 x $20 = $400. $1000 - $400 = $600. I can't remember the last time I rebuilt an automobile engine for $600. I wonder if I ever did...
Cars are now running better and lasting longer than ever due to electronic ignition and injection. It used to be a banner day if your car hit 100,000 miles without a new engine or least a valve job. Now most of the cars I work on have over 130,000 miles and are just on their third set of spark plugs. If people would shorten their service intervals to more reasonable expectations they would experience cars that seemed to go forever, especially with use of synthetic lubes. I'm not going down that road though, synthetics are great, but the price/performance ratio is skewed...it depends on how long you're going to keep the vehicle. With good service most cars will rot off of their wheels before synthetics pay off.
You can move this to an open forum if you think anyone else wants to read it. It's kinda long-winded even though I tried to keep it simple.
Thanx for the compliment,
Beav
>>>beav, i'm interested to know why around 40-50kmiles?
oil change beyond 3000miles, even fully synthetic??
subaru svx site says our oil change recommend is 7500miles?
thanks, beav. you damn cool man for car.