Is synthetic oil a waste?

My mechanic told me the same thing

Mechanics also tell you to change your oil every 3k miles. frick that noise, you can go a minimum of 5k. I use synthetic and I go about 8k between oil changes on a vehicle with 130k on it; all highway though.

Synthetic oil is awesome. A lot of mechanics suck.

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you'd want a thicker oil (regular 5w30) than a thinner, synthetic oil.

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The fully synthetic I buy says SAE 5W30 on it.

My mechanic told me the opposite while raping me for a $95 oil change. Less time between oil changes - this one I had on Saturday will last 7-8k miles.

Horse poo.

Royal purple synthetic FTW. Change every 10k miles. New oil filter every 5k. Use RP for my transfer case and front/rear diffs as well. Every 50k

I only put about 12 to 15k miles my vehicle a year so I only spend about $120 on oil changes yearly.

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you'd want a thicker oil (regular 5w30) than a thinner, synthetic oil.

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synthetic 5w30 is the same viscosity as regular 5w30

compare an oil change for a car on conventional at 3k and another car on synthetic at 5k. Use the same filter.


you'll see the difference in oil change. one comes out smooth still while the other comes out thick and globular.

Back when I used to piss money away modding my LS1's, I sent off oil for analysis a few times and was shocked at how well Royal Purple and Mobile One were holding up after 10-12k miles.

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than a thinner, synthetic oil.

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This is old wives tale that came out about same time as Mobil 1 was placed on the market site. Synthetic is no thinner than dino. They have to pass the same test.

You want an answer to your question? Never ask a mechanic. They turn wrenches but don't know jack about fluids.

I wrote an article a few years ago on this. I consulted with a Tribologist. Bottom line is miles between oil changes and driving conditions. Do the math according to your own costs.

Here is a good place to start if you want a complete answer.
oil education

I use oil that has less numbers between the number before the W and after the W. Example: I prefer 10W30 over 5W30. Why? The additives used to get these numbers shear as the miles go up. After a few miles the 5W30 tends to act more like a 18 weight vs 10W30 which acts more like a straight 20 W. Here in south La. we can get away with using 10Ws vs 5Ws.

The 10W will stay closer to actual 10W30 longer too. It takes less additive to get that formulation.