Diagnostic Solutions: Extended Oil Change Intervals

Diagnostic Solutions: Extended Oil Change Intervals

Extended oil change intervals are a mixed blessing. On the upside, extended oil change intervals are conserving precious oil and reducing carbon emissions. On the downside, many vehicle owners are forgetting to check their engine's oil level between oil changes. The most common result is an engine ruined by excess accumulations of varnish and sludge due to using motor oils that are not approved by the engine manufacturer.

The Result of Extended Oil Change Intervals Taking Their Toll

Auto manufacturers, in general, are continuing to reduce vehicle maintenance requirements by extending oil change intervals. But extended oil change intervals are a mixed blessing. On the upside, extended oil change intervals are conserving precious oil and reducing carbon emissions. On the downside, many vehicle owners are forgetting to check their engine’s oil level between oil changes.

The most common result is an engine ruined by excess accumulations of varnish and sludge due to using motor oils that are not approved by the engine manufacturer. In less common instances, the engine fails due to low engine oil levels and a subsequent lack of lubrication. Whatever the case, extended oil change intervals are changing how we should recommend and perform scheduled vehicle maintenances.

The oil level sensor obviously warns the driver when the engine oil level is critically low. Although many auto manufacturers install oil level warning systems as standard equipment, many vehicles in the current fleet aren’t so equipped. In other instances, the oil level sensor might not function correctly.

Consequently, it’s always important for the technician to check the engine’s oil level whenever the vehicle is being serviced. If the oil appears very dirty or the oil change interval has nearly expired, an oil change and scheduled service recommendation should be made. 

If the oil appears clean but the level is low, it’s important to know the vehicle owner’s brand preference for engine oil before adding oil. Most won’t know or care, but some owners might prefer using a specific brand of oil. In any case, if the engine oil level is low, always inspect the engine and oil filter for leakage or other signs of oil consumption and make the appropriate service recommendations.


Modern oil life monitors use data from the Powertrain Control Module (PCM), such as calculated engine load, trip length, average operating temperature, etc., to measure oil life. It’s not unusual for oil life monitors to extend oil change intervals to 10,000 or more miles.

The primary issue in dealing with oil life monitors is to ensure that the replacement engine oil meets the manufacturer’s extended mileage requirements. The “generic” 5w-30 oil might, for example, expire at 6,000 miles because neither the base oil nor the additive package meets original equipment (OE) requirements, which results in disastrous consequences.

In a few situations, the oil life monitor might not accurately ­indicate expected oil life. The evidence might be a varnish or sludge accumulation on internal engine parts. Valve train sludge, for example, can often be observed when the engine oil cap is removed for service. Similarly, rust, varnish and sludge can form on the upper portions of the oil dipstick. If varnishing or sludging is apparent, a shorter oil change interval should be recommended.


While lead-free, high-detergent gasoline has dramatically reduced intake port and combustion chamber deposits, modern engine oils are also specially formulated to prevent carbon from forming in the combustion chamber, piston rings from sticking and oil additives from contaminating the catalytic converter.

In particular, modern engines generally use narrow, low-tension piston rings that are fitted very tightly into the piston to increase piston ring sealing and reduce oil consumption. On the upside, low piston ring tension reduces rotating friction and cylinder wear. On the downside, low-tension rings with tight side-gap clearances tend to stick when the incorrect engine oil is used. Therefore, the ability of an engine oil to clean and lubricate the piston ring package is critical.


Oil suppliers have also eliminated zinc and phosphorous-based anti-scuff additives that reduce catalytic converter efficiency. While the elimination of these particular anti-scuff additives has increased camshaft wear on some high-performance pushrod-style engines, it hasn’t affected overhead camshaft engines due to the lower valve spring pressures used on overhead camshaft designs.

On the other hand, some engines equipped with direct fuel injection require a high degree of anti-scuff protection to prevent the camshaft-driven high-pressure fuel pump and camshaft lobe from wearing out. In most cases, oil refiners have gone to much higher quality base oils to prevent wear on the high-pressure fuel pump and cam lobe. Again, it’s vitally important to make sure that the replacement oil is either OE oil or is approved by the OE manufacturer.

As for older, performance pushrod, flat-tappet engines that are not equipped with catalytic converters, specially branded performance oils are available with anti-scuff additives to prevent camshaft and valve lifter wear. In addition, zinc-based “ZDDP” additives are also available to enhance the anti-scuff qualities of over-the-counter motor oils. Again, these oils and additives are not intended for vehicles equipped with catalytic converters.

Neglected oil change intervals can ruin the best engine oils. As engine oil accumulates miles, it becomes contaminated with carbon, water and various acids, all of which are a by-product of internal combustion and which will form a film of black, gooey sludge on the interior parts of the engine.

Photo 1: While the slightly varnished interior of this engine is normal, the varnish might not have accumulated if the oil change intervals had been shortened.

Cold-engine operation accelerates the formation of sludge because the oil temperatures aren’t sufficient to evaporate accumulated moisture. Oil sludging is also aggravated by short-trip, cold-weather driving and by thermostats that are stuck open. See Photo 1.

When the engine is operated at high speeds and temperatures, sludge often dislodges and clogs the oil filter. Since most oil filters incorporate bypass valves that allow the lubricating oil to flow around a clogged filter media, the dirty oil can pass directly into the engine and clog small-diameter oil galleries.



Photo 2: A loss of lubrication quickly scores pistons and other vital engine components.

In any case, heavily sludged oil will eventually clog the engine’s oil pump pickup screen, oil filter and oil galleries. The initial symptoms of oil starvation are engines that become noisy during cold start-up and oil pressure gauges that rise very slowly. Broken timing belts are also symptomatic of oil starvation on overhead camshafts. Because the damage usually includes the crankshaft and piston assemblies, don’t be too eager to quote a cylinder head replacement as the cure for a seized camshaft. See Photo 2.

All too often, the detergents contained in fresh oil will accelerate the clogging of oil pump screens and oil filters by loosening accumulated sludge. Volumes of engine sludge and dirty engine oil also easily clog today’s compact oil filters. If the oil filter bypass valve opens during cold starts, more sludge and dirt will pass into the engine bearings and reciprocating parts. In addition, engine life is drastically shortened when operated at extreme loads and temperatures with badly degraded engine oil. See Photo 3.

Photo 3: Oil filter cutters are handy for detecting metallic debris trapped in the oil filtering media. The duct tape helps the filter wrench grip the filter canister.

The problem with any heavily sludged engine is that internal repairs tend to dislodge even more sludge into the oil stream. Because attempting to clean an engine in-chassis is both expensive and risky, you can best address the situation by replacing or rebuilding the engine.

Most modern engines are very susceptible to lubrication problems because they are equipped with variable valve timing (VVT). A pulse-modulated control valve that meters oil pressure to a hydraulic piston or vane-type camshaft timing phaser controls the amount of advance or retard. A separate valve-timing sensor is used to monitor VVT position.

Quite clearly, the phaser must react to small changes in oil pressure. Since sludge can interfere with the smooth modulation of the oil pressure contained inside the cam phaser, the result can be poor engine performance at specific engine speeds and loads. In many cases, a DTC will be stored that indicates a problem in the VVT system.

Since oil prices have climbed dramatically the past few years, customers are becoming more price-sensitive. But it’s also important to understand that, to remain profitable, a shop’s pricing structure for modern vehicle oil change and inspection intervals must be realistic.

In addition, you’re doing a disservice to your import customers if you’re exclusively selling low-cost generic engine oils and budget-priced oil filters to meet price-sensitive competition.

OE-specification oils and filters often become the cheaper (and wiser) choice when weighed against a costly engine replacement. If you do the math, it will become clear to you and your customer that using the correct engine oil and filter is the less expensive and far more prudent choice.

You May Also Like

FCS Introduces 42 New Numbers in May

Complete strut assemblies, shock absorbers, shock absorber assembly kits and suspension struts for popular VIO applications are included.

FCS Automotive announced the release of 42 new numbers in May, including:

8 Complete Strut Assemblies (936,389 vehicles in operation)

6 Shock Absorber Assembly Kits (2,696,801vehicles in operation)

16 Shock Absorbers (6,245,071 vehicles in operation)

12 Suspension Struts (2,135,974 vehicles in operation)

Philips Ultinon Drive 5000 LED Lightbar Line Expands

Lumileds has expanded the Philips Ultinon Drive 5000 series to include eight models.

DMA Adds New BrakeMaster Coverage

New coverage for Ford and Chevy includes popular pickup trucks and SUVs.

Akebono Expands Severe Duty Disc Brake Pad Kits

Akebono said it expanded its severe-duty ultra-premium disc brake pad line by 14 new part numbers.

GSP Releases New CV Axle Part Numbers

GSP said 14 new CV axle part numbers are in stock and ready to ship.

Other Posts

BCA Bearings Unveils 2024 Endless Summer Promotion

The Endless Summer promotion runs from May 1 through June 30, 2024.

PRT Launches 30 New Complete Strut Assemblies

The new items represent more than 10 million vehicles in new coverage, PRT said.

RNR Tire Express Hosts Mother’s Day Giveaway

The eighth-annual event promises $100,000 in prizes, as well as a brand new 2024 Buick Encore for one select nominee.

Brand Refresh for Tires Plus, Hibdon Tires Plus Begins

Logo updates include a single-color tire mark; a logo palette comprised of Tires Plus yellow, black and red; and refined typefaces.