50/50 or Synthetic oil does not break down over time like traditional oil. So mileage is important for both types of oil... but Age only matters more with traditional oil... as it will sludge up after a year or two... Synthetic will not... BUT never wait a year for either. Even if it's not hit 6K miles in that time... best to get fresh oil within a year on Synthetic... and don't chance a year on traditional... it may not sludge but will stick and thicken especially with small amounts of petroleum contamination. Luckily most places use Synthetic now... can you wait 9 months to a year on a car you drove 3500 miles ... only if it's synthetic.... if it's not Synthetic 6 months max for less chances of thickened oil. Also traditional oil will tend to degrade faster once exposed to your engine petroleum and heat. So mileage both... and age 6mo traditional ...12 months Synthetic... are about as much as I would push it if you want a clean cam shaft.
Not necessarily. You should take both into account when purchasing a vehicle.
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