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View Full Version : How do you all get 6.2s to 300K miles?



Nycxjeremyy
04-13-2025, 11:20
I hear often about 6.2 Detroits going to 300K miles and more, but can they really do that? My 1990 K5 Blazer with a swapped in 1985 6.2 Detroit Diesel w/h the ATS Turbo Kit which is at 85K miles (the vehicle itself has 279K miles) ... Already have quite a few in it with the following:

Fluidampr swap from harmonic balancer
4 row Aluminum Radiator
4L60E Transmission (plus a Hayden external cooler)
Spin on filter + water separator
Radio + sound system
Transmission temp guage
That and other miscellaneous stuff such as new seals, bushings, window motors, hoses, mechanical stuff, new grill, etc.

The engine and transmission are fine (except for the engine leaking oil part), but this is all just normal wear and tear for a 40 year old vehicle, I just use it for regular plain old driving, no towing or anything.

I live on my installation, where damn near all my daily trips are within a 2-4 mile radius, so as of now, I change my oil every 3K miles. I use the Rotella T4 varient as (as stated prior) I leak quite a bit. Though if any other options are better, please do tell.

But for those who own similar applications, what do you all do to keep these vehicles going?

(Photos of said vehicle, including paperwork from previous owner:

https://photos.app.goo.gl/ksTMNAVU6ra73RpK9 )

DmaxMaverick
04-13-2025, 13:05
My 85 blazer did that, twice and then some, on the original long block. Head gaskets replaced about mid way (for maintenance purpose, no leaks), and a diet of synthetic oil every 5K miles, whether it needed it or not. No turbo, but the pump was turned up as far as the heat would allow. Most trips were long enough to get it fully up to temp. It had no easy days, and it never knew it wasn't a 1-ton. It was semi-retired in 2001, then parked awaiting a resto in about 2010. The last 10 years put less than 10K miles on it. It's used up, for sure, but will still run today with a minor refresh (batteries, underhood rubber, etc.), although I wouldn't drive it as it is.

Robyn
04-14-2025, 06:58
Maintenance is the key for sure.
As Maverick said.....
Replacing head gaskets (I consider these to be a "Consumable" )
Keeping fresh antifreeze in the cooling system is also a great way to lengthen the head gasket life....Coolant loses it's additive package over time...Plus if the Glycol is mixed with Nasty water that has a lot of minerals in it (TAP WATER IN MANY PLACES) can cause corrosion and degradation of the metal rings on the gaskets and also the block deck surface...

Oil changes.....Diesels get a lot of carbon in the oil.....This stuff is abrasive to a degree and causes wear.....

A good high grade diesel rated oil is paramount....Some folks just grab whats on sale at the MART STORE and Good to go.....

Sludge and other junk wreaks havoc on these engines.
Common to see rings stuck causing a lot of blow by...

Clean....Very clean fuel helps keep the injectors and the IP in good order.
Air filters....Keep them fresh.

THESE THINGS...plus a bit of luck....The high numbers of miles are quite possible...

DieselDavy
04-24-2025, 13:23
I (and my kids) drove my '82 6.2 to 345K miles. I changed the head gaskets only once at about 300k. Started and ran great. Had plenty of blowby but still was a good runner and great on MPGs.
I only got rid of it because it really needed a new truck under it!
I have a line on another '82 for a beater truck. Pretty cool trucks for sure....
d

arveetek
04-24-2025, 13:43
I (and my kids) drove my '82 6.2 to 345K miles. I changed the head gaskets only once at about 300k. Started and ran great. Had plenty of blowby but still was a good runner and great on MPGs.
I only got rid of it because it really needed a new truck under it!
I have a line on another '82 for a beater truck. Pretty cool trucks for sure....
d

How many miles have you got on your 2 door now?

Casey