• Detroit Diesel Corp.
• Fiat Chrysler Automobiles
• Ford Motor Co.
• General Motors Co.
• Honda Motor Co.
• Navistar Inc.
• Toyota Motor Corp.
• Volkswagen AG
The Top Tier designation applies only to certain
gasoline and diesel fuels.
The Top Tier Detergent Gasoline program focuses on
performance of deposit control fuel additives.
The Top Tier Diesel Fuel program includes requirements for deposit control, lubricity and stability, in
addition to station housekeeping measures for water and
The gasoline program came about in 2004 to address
emerging deposit buildup issues. Fuel detergency levels
in the U.S. fuel market had begun dropping quickly
and unexpectedly in 1997 when the Environmental
Protection Agency (EPA) lowest additive concentration
(LAC) for deposit control took effect (see Figure 1).
Initially, fueling experts praised the EPA’s proactive
approach to keep engines clean and enable optimal
engine performance. Many automotive companies, however, began reporting unusual formation of deposits in
their engines. They concluded that the EPA standard isn’t
high enough to prevent engine deposits.
After unsuccessful attempts to prevent deposit buildup
through stricter fuel standards or regulation, four automotive companies created the Top Tier program. The
goal was to create an easily identi;able logo that represents a higher standard in detergency — the one that’s
accepted, recommended and enforced by automotive
A case study involving a 1993 Buick Regal demonstrates why automotive companies desire a higher
standard for engine deposit control (see Figure 2). The
photos depict the results of using two levels of detergency.
The left photo is of an intake valve used in conjunction
with fuel that meets the U.S. minimum required treat
ourteen years after the development of the voluntary Top
Tier gasoline performance standard, common questions
about the program still exist: What is Top Tier? Why
don’t auto companies change the required standards or drive
changes in the regulations? Can’t I just buy premium fuel?
How can my retail station or stations sign up for Top Tier?
Most of the questions come from the general public, but
stakeholders within the fueling industry have questions, too.
The best way to answer the most common Top Tier questions
is with photos and data from case studies.
WHAT IS TOP TIER?
Top Tier is a voluntary fuel standard that requires higher
detergency levels than the federal requirement. The higher Top
Tier standard is proven to keep vehicle engines cleaner and performing as designed. Eleven auto manufacturers recommend in
their owners manuals the use of Top Tier fuels in their vehicles:
• Audi AG
• BMW Group
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