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Old 01-25-2013, 03:19 AM
1project2many 1project2many is offline
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Join Date: Jan 2013
Location: Lakes Region, NH
Posts: 179
Looking at the numbers it's fairly easy to do a simple cost analysis for synthetic vs conventional oil. Rotella synthetic at $27.99 / gallon is about 55% higher than Delvac at $17.99. Increasing the drain interval by 55% to offset the cost means changing oil at 7750 miles instead of 5k, easily achieved by synthetics in most diesels. If we accept that most operating conditions for our engines do not require any other special advantages offered by synthetic oil then we've kept the lifetime cost of oil the same while achieving fewer oil changes.

But I often have a different take when asked about switching to synthetics. In this area we have high humidity, high winter salt usage, and some very rough roads. From this tech's perspective the cost of extended drain intervals on older vehicles in this market seems to be more surprise repairs involving more work and larger shop tickets. I counter the argument to spend more on synthetics by suggesting that using the oil change as a chance to check the car front to back means you're more likely to catch problems before they become major issues. If a DIY person feels there's a correlation between spending money and improving the perceived level of protection I'll recommend reducing drain intervals by 10%, staying with conventional oil, and dedicating an extra 1/2 hr with each oil change to inspecting other areas of the car. With poor quality replacement parts flooding the market I sometimes feel like I should be checking for problems weekly anyway.

Oil analysis is inexpensive and easy and can help you get much more than warm fuzzies from your maintenance program.
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