Even in the 70's & 80's 3000mile/3mo interval for most cars was
push by rip offs like Jiffy Lube.
Problem is people still believe this same crap.
Notice the highlight word...
Mainly... Most vehicle
are not "mainly" driven under the condition listed in Schedule 1 aka Severe Duty
Most people should use Schedule 2, 7,500mile/12mo interval.
Most cars and light trucks in 70's - 80's have same data in their owner book and FSM too but Jiffy Lube et al completely ignores this and use 3000mile BS.
Side note: First 2 conditions are because oil won't heat enough to drive out condensation from moisture in air as engine cools down and gas from running it. Oil can look like coolant leak problem but any gas/water buildup in the oil is bad for the engine. That Lady that drives to church etc a few block away as many Used Car jokes can actually hurt the car because of this.
Many Car makers now call for 5-15 thousands mile change intervals even for "Severe use" vehicles. Data can often will change by brand and model so Read the Owner Manual. Example: 07 Kia Sportage OM call for 5000mile/4mo for all driving and doesn't bother w/ charts like above.
Please ignore M1 "Annual Protection" and any others "extended" oil. May work but is best for another topic. Like M1 likely requires M1 best filter for M1 warranty etc. Stay w/ Dealer and owners book data.
Stop Changing Your Oil! Breaking the 3,000-Mile Habit edmunds
Stop Changing the Oil Every 3,000 Miles Already! Time
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Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should.
(Jurassic Park)The Ogre's Fiero Cave[This message has been edited by theogre (edited 11-07-2017).]